1 ------------------------------------------------------------------------------
3 -- GNAT RUN-TIME COMPONENTS --
5 -- A D A . C A L E N D A R --
9 -- Copyright (C) 1992-2007, Free Software Foundation, Inc. --
11 -- This specification is derived from the Ada Reference Manual for use with --
12 -- GNAT. The copyright notice above, and the license provisions that follow --
13 -- apply solely to the contents of the part following the private keyword. --
15 -- GNAT is free software; you can redistribute it and/or modify it under --
16 -- terms of the GNU General Public License as published by the Free Soft- --
17 -- ware Foundation; either version 2, or (at your option) any later ver- --
18 -- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
19 -- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
20 -- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
21 -- for more details. You should have received a copy of the GNU General --
22 -- Public License distributed with GNAT; see file COPYING. If not, write --
23 -- to the Free Software Foundation, 51 Franklin Street, Fifth Floor, --
24 -- Boston, MA 02110-1301, USA. --
26 -- As a special exception, if other files instantiate generics from this --
27 -- unit, or you link this unit with other files to produce an executable, --
28 -- this unit does not by itself cause the resulting executable to be --
29 -- covered by the GNU General Public License. This exception does not --
30 -- however invalidate any other reasons why the executable file might be --
31 -- covered by the GNU Public License. --
33 -- GNAT was originally developed by the GNAT team at New York University. --
34 -- Extensive contributions were provided by Ada Core Technologies Inc. --
36 ------------------------------------------------------------------------------
38 package Ada.Calendar is
42 -- Declarations representing limits of allowed local time values. Note that
43 -- these do NOT constrain the possible stored values of time which may well
44 -- permit a larger range of times (this is explicitly allowed in Ada 95).
46 subtype Year_Number is Integer range 1901 .. 2399;
47 subtype Month_Number is Integer range 1 .. 12;
48 subtype Day_Number is Integer range 1 .. 31;
50 -- A Day_Duration value of 86_400.0 designates a new day
52 subtype Day_Duration is Duration range 0.0 .. 86_400.0;
54 function Clock return Time;
55 -- The returned time value is the number of nanoseconds since the start
56 -- of Ada time (1901-01-01 00:00:00.0 UTC).
58 function Year (Date : Time) return Year_Number;
59 function Month (Date : Time) return Month_Number;
60 function Day (Date : Time) return Day_Number;
61 function Seconds (Date : Time) return Day_Duration;
65 Year : out Year_Number;
66 Month : out Month_Number;
68 Seconds : out Day_Duration);
69 -- Break down a time value into its date components set in the current
70 -- time zone. If Split is called on a time value created using Ada 2005
71 -- Time_Of in some arbitrary time zone, the input value will always be
72 -- interpreted as relative to the local time zone.
78 Seconds : Day_Duration := 0.0) return Time;
79 -- GNAT Note: Normally when procedure Split is called on a Time value
80 -- result of a call to function Time_Of, the out parameters of procedure
81 -- Split are identical to the in parameters of function Time_Of. However,
82 -- when a non-existent time of day is specified, the values for Seconds
83 -- may or may not be different. This may happen when Daylight Saving Time
84 -- (DST) is in effect, on the day when switching to DST, if Seconds
85 -- specifies a time of day in the hour that does not exist. For example,
88 -- Time_Of (Year => 1998, Month => 4, Day => 5, Seconds => 10740.0)
90 -- will return a Time value T. If Split is called on T, the resulting
91 -- Seconds may be 14340.0 (3:59:00) instead of 10740.0 (2:59:00 being
92 -- a time that not exist).
94 function "+" (Left : Time; Right : Duration) return Time;
95 function "+" (Left : Duration; Right : Time) return Time;
96 function "-" (Left : Time; Right : Duration) return Time;
97 function "-" (Left : Time; Right : Time) return Duration;
98 -- The first three functions will raise Time_Error if the resulting time
99 -- value is less than the start of Ada time in UTC or greater than the
100 -- end of Ada time in UTC. The last function will raise Time_Error if the
101 -- resulting difference cannot fit into a duration value.
103 function "<" (Left, Right : Time) return Boolean;
104 function "<=" (Left, Right : Time) return Boolean;
105 function ">" (Left, Right : Time) return Boolean;
106 function ">=" (Left, Right : Time) return Boolean;
108 Time_Error : exception;
111 pragma Inline (Clock);
113 pragma Inline (Year);
114 pragma Inline (Month);
121 pragma Inline ("<=");
123 pragma Inline (">=");
125 -- The units used in this version of Ada.Calendar are nanoseconds. The
126 -- following constants provide values used in conversions of seconds or
127 -- days to the underlying units.
129 Nano : constant := 1_000_000_000;
130 Nano_F : constant := 1_000_000_000.0;
131 Nanos_In_Day : constant := 86_400_000_000_000;
132 Secs_In_Day : constant := 86_400;
134 ----------------------------
135 -- Implementation of Time --
136 ----------------------------
138 -- Time is represented as a signed 64 bit integer count of nanoseconds
139 -- since the start of Ada time (1901-01-01 00:00:00.0 UTC). Time values
140 -- produced by Time_Of are internaly normalized to UTC regardless of their
141 -- local time zone. This representation ensures correct handling of leap
142 -- seconds as well as performing arithmetic. In Ada 95, Split and Time_Of
143 -- will treat a time value as being in the local time zone, in Ada 2005,
144 -- Split and Time_Of will treat a time value as being in the designated
145 -- time zone by the formal parameter or in UTC by default. The size of the
146 -- type is large enough to cover the Ada 2005 range of time (1901-01-01
147 -- 00:00:00.0 UTC - 2399-12-31-23:59:59.999999999 UTC).
153 -- Due to Earth's slowdown, the astronomical time is not as precise as the
154 -- International Atomic Time. To compensate for this inaccuracy, a single
155 -- leap second is added after the last day of June or December. The count
156 -- of seconds during those occurences becomes:
158 -- ... 58, 59, leap second 60, 0, 1, 2 ...
160 -- Unlike leap days, leap seconds occur simultaneously around the world.
161 -- In other words, if a leap second occurs at 23:59:60 UTC, it also occurs
162 -- on 18:59:60 -5 the same day or 2:59:60 +2 on the next day.
164 -- Leap seconds do not follow a formula. The International Earth Rotation
165 -- and Reference System Service decides when to add one. Leap seconds are
166 -- included in the representation of time in Ada 95 mode. As a result,
167 -- the following two time values will differ by two seconds:
169 -- 1972-06-30 23:59:59.0
170 -- 1972-07-01 00:00:00.0
172 -- When a new leap second is added, the following steps must be carried
175 -- 1) Increment Leap_Seconds_Count by one
176 -- 2) Add an entry to the end of table Leap_Second_Dates
178 -- The algorithms that build the actual leap second values and discover
179 -- how many leap seconds have occured between two dates do not need any
182 ------------------------------
183 -- Non-leap centenial years --
184 ------------------------------
186 -- Over the range of Ada time, centenial years 2100, 2200 and 2300 are
187 -- non-leap. As a consequence, seven non-leap years occur over the period
188 -- of year - 4 to year + 4. Internaly, routines Split and Time_Of add or
189 -- subtract a "fake" February 29 to facilitate the arithmetic involved.
191 -- The underlying type of Time has been chosen to be a 64 bit signed
192 -- integer number since it allows for easier processing of sub seconds
195 type Time_Rep is range -2 ** 63 .. +2 ** 63 - 1;
196 type Time is new Time_Rep;
198 Days_In_Month : constant array (Month_Number) of Day_Number :=
199 (31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31);
201 Invalid_Time_Zone_Offset : Long_Integer;
202 pragma Import (C, Invalid_Time_Zone_Offset, "__gnat_invalid_tzoff");
204 function Is_Leap (Year : Year_Number) return Boolean;
205 -- Determine whether a given year is leap
207 -- The following packages provide a target independent interface to the
208 -- children of Calendar - Arithmetic, Delays, Formatting and Time_Zones.
210 package Arithmetic_Operations is
211 function Add (Date : Time; Days : Long_Integer) return Time;
212 -- Add a certain number of days to a time value
217 Days : out Long_Integer;
218 Seconds : out Duration;
219 Leap_Seconds : out Integer);
220 -- Calculate the difference between two time values in terms of days,
221 -- seconds and leap seconds elapsed. The leap seconds are not included
222 -- in the seconds returned. If Left is greater than Right, the returned
223 -- values are positive, negative otherwise.
225 function Subtract (Date : Time; Days : Long_Integer) return Time;
226 -- Subtract a certain number of days from a time value
227 end Arithmetic_Operations;
229 package Delays_Operations is
230 function To_Duration (Date : Time) return Duration;
231 -- Given a time value in nanoseconds since 1901, convert it into a
232 -- duration value giving the number of nanoseconds since the Unix Epoch.
233 end Delays_Operations;
235 package Formatting_Operations is
236 function Day_Of_Week (Date : Time) return Integer;
237 -- Determine which day of week Date falls on. The returned values are
238 -- within the range of 0 .. 6 (Monday .. Sunday).
242 Year : out Year_Number;
243 Month : out Month_Number;
244 Day : out Day_Number;
245 Day_Secs : out Day_Duration;
247 Minute : out Integer;
248 Second : out Integer;
249 Sub_Sec : out Duration;
250 Leap_Sec : out Boolean;
252 Time_Zone : Long_Integer);
253 -- Split a time value into its components. Set Is_Ada_05 to use the
254 -- local time zone (the value in Time_Zone is ignored) when splitting
259 Month : Month_Number;
261 Day_Secs : Day_Duration;
267 Use_Day_Secs : Boolean;
269 Time_Zone : Long_Integer) return Time;
270 -- Given all the components of a date, return the corresponding time
271 -- value. Set Use_Day_Secs to use the value in Day_Secs, otherwise the
272 -- day duration will be calculated from Hour, Minute, Second and Sub_
273 -- Sec. Set Is_Ada_05 to use the local time zone (the value in formal
274 -- Time_Zone is ignored) when building a time value and to verify the
275 -- validity of a requested leap second.
276 end Formatting_Operations;
278 package Time_Zones_Operations is
279 function UTC_Time_Offset (Date : Time) return Long_Integer;
280 -- Return the offset in seconds from UTC
281 end Time_Zones_Operations;