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1 ------------------------------------------------------------------------------
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2 -- --
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3 -- GNAT RUN-TIME COMPONENTS --
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4 -- --
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5 -- A D A . C A L E N D A R --
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6 -- --
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7 -- S p e c --
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8 -- --
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9 -- Copyright (C) 1992-2019, Free Software Foundation, Inc. --
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10 -- --
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11 -- This specification is derived from the Ada Reference Manual for use with --
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12 -- GNAT. The copyright notice above, and the license provisions that follow --
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13 -- apply solely to the contents of the part following the private keyword. --
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14 -- --
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15 -- GNAT is free software; you can redistribute it and/or modify it under --
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16 -- terms of the GNU General Public License as published by the Free Soft- --
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17 -- ware Foundation; either version 3, or (at your option) any later ver- --
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18 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
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19 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
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20 -- or FITNESS FOR A PARTICULAR PURPOSE. --
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21 -- --
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22 -- As a special exception under Section 7 of GPL version 3, you are granted --
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23 -- additional permissions described in the GCC Runtime Library Exception, --
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24 -- version 3.1, as published by the Free Software Foundation. --
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25 -- --
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26 -- You should have received a copy of the GNU General Public License and --
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27 -- a copy of the GCC Runtime Library Exception along with this program; --
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28 -- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see --
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29 -- <http://www.gnu.org/licenses/>. --
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30 -- --
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31 -- GNAT was originally developed by the GNAT team at New York University. --
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32 -- Extensive contributions were provided by Ada Core Technologies Inc. --
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33 -- --
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34 ------------------------------------------------------------------------------
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35
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36 package Ada.Calendar with
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37 SPARK_Mode,
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38 Abstract_State => (Clock_Time with Synchronous),
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39 Initializes => Clock_Time
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40 is
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41
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42 type Time is private;
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43
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44 -- Declarations representing limits of allowed local time values. Note that
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45 -- these do NOT constrain the possible stored values of time which may well
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46 -- permit a larger range of times (this is explicitly allowed in Ada 95).
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47
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48 subtype Year_Number is Integer range 1901 .. 2399;
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49 subtype Month_Number is Integer range 1 .. 12;
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50 subtype Day_Number is Integer range 1 .. 31;
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51
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52 -- A Day_Duration value of 86_400.0 designates a new day
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53
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54 subtype Day_Duration is Duration range 0.0 .. 86_400.0;
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55
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56 function Clock return Time with
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57 Volatile_Function,
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58 Global => Clock_Time;
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59 -- The returned time value is the number of nanoseconds since the start
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60 -- of Ada time (1901-01-01 00:00:00.0 UTC). If leap seconds are enabled,
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61 -- the result will contain all elapsed leap seconds since the start of
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62 -- Ada time until now.
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63
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64 function Year (Date : Time) return Year_Number;
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65 function Month (Date : Time) return Month_Number;
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66 function Day (Date : Time) return Day_Number;
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67 function Seconds (Date : Time) return Day_Duration;
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68 -- SPARK Note: These routines, just like Split and Time_Of below, might use
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69 -- the OS-specific timezone database that is typically stored in a file.
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70 -- This side effect needs to be modeled, so there is no Global => null.
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71
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72 procedure Split
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73 (Date : Time;
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74 Year : out Year_Number;
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75 Month : out Month_Number;
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76 Day : out Day_Number;
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77 Seconds : out Day_Duration);
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78 -- Break down a time value into its date components set in the current
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79 -- time zone. If Split is called on a time value created using Ada 2005
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80 -- Time_Of in some arbitrary time zone, the input value will always be
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81 -- interpreted as relative to the local time zone.
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82
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83 function Time_Of
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84 (Year : Year_Number;
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85 Month : Month_Number;
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86 Day : Day_Number;
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87 Seconds : Day_Duration := 0.0) return Time;
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88 -- GNAT Note: Normally when procedure Split is called on a Time value
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89 -- result of a call to function Time_Of, the out parameters of procedure
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90 -- Split are identical to the in parameters of function Time_Of. However,
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91 -- when a non-existent time of day is specified, the values for Seconds
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92 -- may or may not be different. This may happen when Daylight Saving Time
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93 -- (DST) is in effect, on the day when switching to DST, if Seconds
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94 -- specifies a time of day in the hour that does not exist. For example,
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95 -- in New York:
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96 --
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97 -- Time_Of (Year => 1998, Month => 4, Day => 5, Seconds => 10740.0)
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98 --
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99 -- will return a Time value T. If Split is called on T, the resulting
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100 -- Seconds may be 14340.0 (3:59:00) instead of 10740.0 (2:59:00 being
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101 -- a time that not exist).
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102
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103 function "+" (Left : Time; Right : Duration) return Time
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104 with
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105 Global => null;
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106 function "+" (Left : Duration; Right : Time) return Time
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107 with
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108 Global => null;
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109 function "-" (Left : Time; Right : Duration) return Time
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110 with
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111 Global => null;
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112 function "-" (Left : Time; Right : Time) return Duration
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113 with
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114 Global => null;
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115 -- The first three functions will raise Time_Error if the resulting time
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116 -- value is less than the start of Ada time in UTC or greater than the
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117 -- end of Ada time in UTC. The last function will raise Time_Error if the
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118 -- resulting difference cannot fit into a duration value.
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119
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120 function "<" (Left, Right : Time) return Boolean with Global => null;
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121 function "<=" (Left, Right : Time) return Boolean with Global => null;
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122 function ">" (Left, Right : Time) return Boolean with Global => null;
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123 function ">=" (Left, Right : Time) return Boolean with Global => null;
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124
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125 Time_Error : exception;
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126
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127 private
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128 -- Mark the private part as SPARK_Mode Off to avoid accounting for variable
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129 -- Invalid_Time_Zone_Offset in abstract state.
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130
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131 pragma SPARK_Mode (Off);
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132
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133 pragma Inline (Clock);
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134
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135 pragma Inline (Year);
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136 pragma Inline (Month);
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137 pragma Inline (Day);
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138
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139 pragma Inline ("+");
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140 pragma Inline ("-");
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141
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142 pragma Inline ("<");
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143 pragma Inline ("<=");
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144 pragma Inline (">");
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145 pragma Inline (">=");
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146
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147 -- The units used in this version of Ada.Calendar are nanoseconds. The
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148 -- following constants provide values used in conversions of seconds or
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149 -- days to the underlying units.
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150
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151 Nano : constant := 1_000_000_000;
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152 Nano_F : constant := 1_000_000_000.0;
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153 Nanos_In_Day : constant := 86_400_000_000_000;
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154 Secs_In_Day : constant := 86_400;
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155
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156 ----------------------------
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157 -- Implementation of Time --
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158 ----------------------------
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159
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160 -- Time is represented as a signed 64 bit integer count of nanoseconds
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161 -- since the start of Ada time (1901-01-01 00:00:00.0 UTC). Time values
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162 -- produced by Time_Of are internally normalized to UTC regardless of their
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163 -- local time zone. This representation ensures correct handling of leap
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164 -- seconds as well as performing arithmetic. In Ada 95, Split and Time_Of
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165 -- will treat a time value as being in the local time zone, in Ada 2005,
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166 -- Split and Time_Of will treat a time value as being in the designated
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167 -- time zone by the formal parameter or in UTC by default. The size of the
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168 -- type is large enough to cover the Ada 2005 range of time (1901-01-01
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169 -- 00:00:00.0 UTC - 2399-12-31-23:59:59.999999999 UTC).
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170
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171 ------------------
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172 -- Leap Seconds --
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173 ------------------
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174
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175 -- Due to Earth's slowdown, the astronomical time is not as precise as the
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176 -- International Atomic Time. To compensate for this inaccuracy, a single
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177 -- leap second is added after the last day of June or December. The count
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178 -- of seconds during those occurrences becomes:
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179
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180 -- ... 58, 59, leap second 60, 0, 1, 2 ...
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181
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182 -- Unlike leap days, leap seconds occur simultaneously around the world.
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183 -- In other words, if a leap second occurs at 23:59:60 UTC, it also occurs
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184 -- on 18:59:60 -5 the same day or 2:59:60 +2 on the next day.
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185
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186 -- Leap seconds do not follow a formula. The International Earth Rotation
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187 -- and Reference System Service decides when to add one. Leap seconds are
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188 -- included in the representation of time in Ada 95 mode. As a result,
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189 -- the following two time values will differ by two seconds:
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190
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191 -- 1972-06-30 23:59:59.0
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192 -- 1972-07-01 00:00:00.0
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193
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194 -- When a new leap second is introduced, the following steps must be
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195 -- carried out:
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196
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197 -- 1) Increment Leap_Seconds_Count in a-calend.adb by one
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198 -- 2) Increment LS_Count in xleaps.adb by one
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199 -- 3) Add the new date to the aggregate of array LS_Dates in
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200 -- xleaps.adb
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201 -- 4) Compile and execute xleaps
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202 -- 5) Replace the values of Leap_Second_Times in a-calend.adb with the
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203 -- aggregate generated by xleaps
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204
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205 -- The algorithms that build the actual leap second values and discover
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206 -- how many leap seconds have occurred between two dates do not need any
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207 -- modification.
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208
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209 ------------------------------
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210 -- Non-leap Centennial Years --
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211 ------------------------------
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212
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213 -- Over the range of Ada time, centennial years 2100, 2200 and 2300 are
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214 -- non-leap. As a consequence, seven non-leap years occur over the period
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215 -- of year - 4 to year + 4. Internally, routines Split and Time_Of add or
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216 -- subtract a "fake" February 29 to facilitate the arithmetic involved.
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217
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218 ------------------------
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219 -- Local Declarations --
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220 ------------------------
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221
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222 type Time_Rep is new Long_Long_Integer;
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223 type Time is new Time_Rep;
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224 -- The underlying type of Time has been chosen to be a 64 bit signed
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225 -- integer number since it allows for easier processing of sub-seconds
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226 -- and arithmetic. We use Long_Long_Integer to allow this unit to compile
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227 -- when using custom target configuration files where the max integer is
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228 -- 32 bits. This is useful for static analysis tools such as SPARK or
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229 -- CodePeer.
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230 --
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231 -- Note: the reason we have two separate types here is to avoid problems
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232 -- with overloading ambiguities in the body if we tried to use Time as an
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233 -- internal computational type.
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234
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235 function Epoch_Offset return Time_Rep;
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236 pragma Inline (Epoch_Offset);
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237 -- Return the difference between 2150-1-1 UTC and 1970-1-1 UTC expressed in
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238 -- nanoseconds. Note that year 2100 is non-leap.
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239
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240 Days_In_Month : constant array (Month_Number) of Day_Number :=
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241 (31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);
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242 -- Days in month for non-leap year, leap year case is adjusted in code
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243
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244 Invalid_Time_Zone_Offset : Long_Integer;
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245 pragma Import (C, Invalid_Time_Zone_Offset, "__gnat_invalid_tzoff");
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246
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247 function Is_Leap (Year : Year_Number) return Boolean;
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248 -- Determine whether a given year is leap
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249
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250 ----------------------------------------------------------
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251 -- Target-Independent Interface to Children of Calendar --
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252 ----------------------------------------------------------
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253
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254 -- The following packages provide a target-independent interface to the
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255 -- children of Calendar - Arithmetic, Conversions, Delays, Formatting and
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256 -- Time_Zones.
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257
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258 ---------------------------
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259 -- Arithmetic_Operations --
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260 ---------------------------
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261
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262 package Arithmetic_Operations is
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263
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264 function Add (Date : Time; Days : Long_Integer) return Time;
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265 -- Add a certain number of days to a time value
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266
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267 procedure Difference
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268 (Left : Time;
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269 Right : Time;
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270 Days : out Long_Integer;
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271 Seconds : out Duration;
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272 Leap_Seconds : out Integer);
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273 -- Calculate the difference between two time values in terms of days,
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274 -- seconds and leap seconds elapsed. The leap seconds are not included
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275 -- in the seconds returned. If Left is greater than Right, the returned
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276 -- values are positive, negative otherwise.
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277
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278 function Subtract (Date : Time; Days : Long_Integer) return Time;
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279 -- Subtract a certain number of days from a time value
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280
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281 end Arithmetic_Operations;
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282
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283 ---------------------------
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284 -- Conversion_Operations --
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285 ---------------------------
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286
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287 package Conversion_Operations is
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288
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289 function To_Ada_Time (Unix_Time : Long_Integer) return Time;
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290 -- Unix to Ada Epoch conversion
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291
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292 function To_Ada_Time
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293 (tm_year : Integer;
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294 tm_mon : Integer;
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295 tm_day : Integer;
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296 tm_hour : Integer;
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297 tm_min : Integer;
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298 tm_sec : Integer;
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299 tm_isdst : Integer) return Time;
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300 -- Struct tm to Ada Epoch conversion
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301
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302 function To_Duration
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303 (tv_sec : Long_Integer;
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304 tv_nsec : Long_Integer) return Duration;
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305 -- Struct timespec to Duration conversion
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306
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307 procedure To_Struct_Timespec
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308 (D : Duration;
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309 tv_sec : out Long_Integer;
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310 tv_nsec : out Long_Integer);
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311 -- Duration to struct timespec conversion
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312
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313 procedure To_Struct_Tm
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314 (T : Time;
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315 tm_year : out Integer;
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316 tm_mon : out Integer;
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317 tm_day : out Integer;
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318 tm_hour : out Integer;
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319 tm_min : out Integer;
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320 tm_sec : out Integer);
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321 -- Time to struct tm conversion
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322
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323 function To_Unix_Time (Ada_Time : Time) return Long_Integer;
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324 -- Ada to Unix Epoch conversion
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325
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326 end Conversion_Operations;
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327
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328 ----------------------
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329 -- Delay_Operations --
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330 ----------------------
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331
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332 package Delay_Operations is
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333
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334 function To_Duration (Date : Time) return Duration;
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335 -- Given a time value in nanoseconds since 1901, convert it into a
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336 -- duration value giving the number of nanoseconds since the Unix Epoch.
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337
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338 end Delay_Operations;
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339
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340 ---------------------------
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341 -- Formatting_Operations --
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342 ---------------------------
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343
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344 package Formatting_Operations is
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345
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346 function Day_Of_Week (Date : Time) return Integer;
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347 -- Determine which day of week Date falls on. The returned values are
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348 -- within the range of 0 .. 6 (Monday .. Sunday).
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349
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350 procedure Split
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351 (Date : Time;
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352 Year : out Year_Number;
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353 Month : out Month_Number;
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354 Day : out Day_Number;
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355 Day_Secs : out Day_Duration;
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356 Hour : out Integer;
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357 Minute : out Integer;
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358 Second : out Integer;
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359 Sub_Sec : out Duration;
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360 Leap_Sec : out Boolean;
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361 Use_TZ : Boolean;
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362 Is_Historic : Boolean;
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363 Time_Zone : Long_Integer);
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364 pragma Export (Ada, Split, "__gnat_split");
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365 -- Split a time value into its components. If flag Is_Historic is set,
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366 -- this routine would try to use to the best of the OS's abilities the
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367 -- time zone offset that was or will be in effect on Date. Set Use_TZ
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368 -- to use the local time zone (the value in Time_Zone is ignored) when
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369 -- splitting a time value.
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370
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371 function Time_Of
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372 (Year : Year_Number;
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373 Month : Month_Number;
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374 Day : Day_Number;
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375 Day_Secs : Day_Duration;
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376 Hour : Integer;
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377 Minute : Integer;
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378 Second : Integer;
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379 Sub_Sec : Duration;
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380 Leap_Sec : Boolean;
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381 Use_Day_Secs : Boolean;
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382 Use_TZ : Boolean;
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383 Is_Historic : Boolean;
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384 Time_Zone : Long_Integer) return Time;
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385 pragma Export (Ada, Time_Of, "__gnat_time_of");
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386 -- Given all the components of a date, return the corresponding time
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387 -- value. Set Use_Day_Secs to use the value in Day_Secs, otherwise the
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388 -- day duration will be calculated from Hour, Minute, Second and Sub_
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389 -- Sec. If flag Is_Historic is set, this routine would try to use to the
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390 -- best of the OS's abilities the time zone offset that was or will be
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391 -- in effect on the input date. Set Use_TZ to use the local time zone
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392 -- (the value in formal Time_Zone is ignored) when building a time value
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393 -- and to verify the validity of a requested leap second.
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394
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395 end Formatting_Operations;
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396
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397 ---------------------------
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398 -- Time_Zones_Operations --
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399 ---------------------------
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400
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401 package Time_Zones_Operations is
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402
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403 function UTC_Time_Offset (Date : Time) return Long_Integer;
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404 -- Return (in seconds) the difference between the local time zone and
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405 -- UTC time at a specific historic date.
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406
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407 end Time_Zones_Operations;
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408
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409 end Ada.Calendar;
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