Ada Conformity Assessment Authority      Home Conformity Assessment   Test Suite ARGAda Standard
 
Ada Reference ManualLegal Information
Contents   Index   References   Search   Previous   Next 

9.6.1 Formatting, Time Zones, and other operations for Time

Static Semantics

1/2
The following language-defined library packages exist:
2/2
package Ada.Calendar.Time_Zones is
3/2
   -- Time zone manipulation:
4/2
   type Time_Offset is range -28*60 .. 28*60;
5/2
   Unknown_Zone_Error : exception;
6/2
   function UTC_Time_Offset (Date : Time := Clock) return Time_Offset;
7/2
end Ada.Calendar.Time_Zones;
8/2

package Ada.Calendar.Arithmetic is
9/2
   -- Arithmetic on days:
10/2
   type Day_Count is range
     -366*(1+Year_Number'Last - Year_Number'First)
     ..
     366*(1+Year_Number'Last - Year_Number'First);
11/2
   subtype Leap_Seconds_Count is Integer range -2047 .. 2047;
12/2
   procedure Difference (Left, Right : in Time;
                         Days : out Day_Count;
                         Seconds : out Duration;
                         Leap_Seconds : out Leap_Seconds_Count);
13/2
   function "+" (Left : Time; Right : Day_Count) return Time;
   function "+" (Left : Day_Count; Right : Time) return Time;
   function "-" (Left : Time; Right : Day_Count) return Time;
   function "-" (Left, Right : Time) return Day_Count;
14/2
end Ada.Calendar.Arithmetic;
15/2

with Ada.Calendar.Time_Zones;
package Ada.Calendar.Formatting is
16/2
   -- Day of the week:
17/2
   type Day_Name is (Monday, Tuesday, Wednesday, Thursday,
       Friday, Saturday, Sunday);
18/2
   function Day_of_Week (Date : Time) return Day_Name;
19/2
   -- Hours:Minutes:Seconds access:
20/2
   subtype Hour_Number         is Natural range 0 .. 23;
   subtype Minute_Number       is Natural range 0 .. 59;
   subtype Second_Number       is Natural range 0 .. 59;
   subtype Second_Duration     is Day_Duration range 0.0 .. 1.0;
21/2
   function Year       (Date : Time;
                        Time_Zone  : Time_Zones.Time_Offset := 0)
                           return Year_Number;
22/2
   function Month      (Date : Time;
                        Time_Zone  : Time_Zones.Time_Offset := 0)
                           return Month_Number;
23/2
   function Day        (Date : Time;
                        Time_Zone  : Time_Zones.Time_Offset := 0)
                           return Day_Number;
24/2
   function Hour       (Date : Time;
                        Time_Zone  : Time_Zones.Time_Offset := 0)
                           return Hour_Number;
25/2
   function Minute     (Date : Time;
                        Time_Zone  : Time_Zones.Time_Offset := 0)
                           return Minute_Number;
26/2
   function Second     (Date : Time)
                           return Second_Number;
27/2
   function Sub_Second (Date : Time)
                           return Second_Duration;
28/2
   function Seconds_Of (Hour   :  Hour_Number;
                        Minute : Minute_Number;
                        Second : Second_Number := 0;
                        Sub_Second : Second_Duration := 0.0)
       return Day_Duration;
29/2
   procedure Split (Seconds    : in Day_Duration;
                    Hour       : out Hour_Number;
                    Minute     : out Minute_Number;
                    Second     : out Second_Number;
                    Sub_Second : out Second_Duration);
30/2
   function Time_Of (Year       : Year_Number;
                     Month      : Month_Number;
                     Day        : Day_Number;
                     Hour       : Hour_Number;
                     Minute     : Minute_Number;
                     Second     : Second_Number;
                     Sub_Second : Second_Duration := 0.0;
                     Leap_Second: Boolean := False;
                     Time_Zone  : Time_Zones.Time_Offset := 0)
                             return Time;
31/2
   function Time_Of (Year       : Year_Number;
                     Month      : Month_Number;
                     Day        : Day_Number;
                     Seconds    : Day_Duration := 0.0;
                     Leap_Second: Boolean := False;
                     Time_Zone  : Time_Zones.Time_Offset := 0)
                             return Time;
32/2
   procedure Split (Date       : in Time;
                    Year       : out Year_Number;
                    Month      : out Month_Number;
                    Day        : out Day_Number;
                    Hour       : out Hour_Number;
                    Minute     : out Minute_Number;
                    Second     : out Second_Number;
                    Sub_Second : out Second_Duration;
                    Time_Zone  : in Time_Zones.Time_Offset := 0);
33/2
   procedure Split (Date       : in Time;
                    Year       : out Year_Number;
                    Month      : out Month_Number;
                    Day        : out Day_Number;
                    Hour       : out Hour_Number;
                    Minute     : out Minute_Number;
                    Second     : out Second_Number;
                    Sub_Second : out Second_Duration;
                    Leap_Second: out Boolean;
                    Time_Zone  : in Time_Zones.Time_Offset := 0);
34/2
   procedure Split (Date       : in Time;
                    Year       : out Year_Number;
                    Month      : out Month_Number;
                    Day        : out Day_Number;
                    Seconds    : out Day_Duration;
                    Leap_Second: out Boolean;
                    Time_Zone  : in Time_Zones.Time_Offset := 0);
35/2
   -- Simple image and value:
   function Image (Date : Time;
                   Include_Time_Fraction : Boolean := False;
                   Time_Zone  : Time_Zones.Time_Offset := 0) return String;
36/2
   function Value (Date : String;
                   Time_Zone  : Time_Zones.Time_Offset := 0) return Time;
37/2
   function Image (Elapsed_Time : Duration;
                   Include_Time_Fraction : Boolean := False) return String;
38/2
   function Value (Elapsed_Time : String) return Duration;
39/2
end Ada.Calendar.Formatting;
40/2
 Type Time_Offset represents the number of minutes difference between the implementation-defined time zone used by Calendar and another time zone.
41/2
function UTC_Time_Offset (Date : Time := Clock) return Time_Offset;
42/3
Returns, as a number of minutes, the result of subtracting the implementation-defined time zone of Calendar from UTC time, at the time Date. If the time zone of the Calendar implementation is unknown, then Unknown_Zone_Error is raised.
43/2
procedure Difference (Left, Right : in Time;
                      Days : out Day_Count;
                      Seconds : out Duration;
                      Leap_Seconds : out Leap_Seconds_Count);
44/2
Returns the difference between Left and Right. Days is the number of days of difference, Seconds is the remainder seconds of difference excluding leap seconds, and Leap_Seconds is the number of leap seconds. If Left < Right, then Seconds <= 0.0, Days <= 0, and Leap_Seconds <= 0. Otherwise, all values are nonnegative. The absolute value of Seconds is always less than 86_400.0. For the returned values, if Days = 0, then Seconds + Duration(Leap_Seconds) = Calendar."–" (Left, Right). 
45/2
function "+" (Left : Time; Right : Day_Count) return Time;
function "+" (Left : Day_Count; Right : Time) return Time;
46/2
Adds a number of days to a time value. Time_Error is raised if the result is not representable as a value of type Time.
47/2
function "-" (Left : Time; Right : Day_Count) return Time;
48/2
Subtracts a number of days from a time value. Time_Error is raised if the result is not representable as a value of type Time.
49/2
function "-" (Left, Right : Time) return Day_Count;
50/2
Subtracts two time values, and returns the number of days between them. This is the same value that Difference would return in Days.
51/2
function Day_of_Week (Date : Time) return Day_Name;
52/2
Returns the day of the week for Time. This is based on the Year, Month, and Day values of Time.
53/2
function Year       (Date : Time;
                     Time_Zone  : Time_Zones.Time_Offset := 0)
                        return Year_Number;
54/2
Returns the year for Date, as appropriate for the specified time zone offset.
55/2
function Month      (Date : Time;
                     Time_Zone  : Time_Zones.Time_Offset := 0)
                        return Month_Number;
56/2
Returns the month for Date, as appropriate for the specified time zone offset.
57/2
function Day        (Date : Time;
                     Time_Zone  : Time_Zones.Time_Offset := 0)
                        return Day_Number;
58/2
Returns the day number for Date, as appropriate for the specified time zone offset.
59/2
function Hour       (Date : Time;
                     Time_Zone  : Time_Zones.Time_Offset := 0)
                        return Hour_Number;
60/2
Returns the hour for Date, as appropriate for the specified time zone offset.
61/2
function Minute     (Date : Time;
                     Time_Zone  : Time_Zones.Time_Offset := 0)
                        return Minute_Number;
62/2
Returns the minute within the hour for Date, as appropriate for the specified time zone offset.
63/2
function Second     (Date : Time)
                        return Second_Number;
64/2
Returns the second within the hour and minute for Date.
65/2
function Sub_Second (Date : Time)
                        return Second_Duration;
66/2
Returns the fraction of second for Date (this has the same accuracy as Day_Duration). The value returned is always less than 1.0.
67/2
function Seconds_Of (Hour   : Hour_Number;
                     Minute : Minute_Number;
                     Second : Second_Number := 0;
                     Sub_Second : Second_Duration := 0.0)
    return Day_Duration;
68/2
Returns a Day_Duration value for the combination of the given Hour, Minute, Second, and Sub_Second. This value can be used in Calendar.Time_Of as well as the argument to Calendar."+" and Calendar."–". If Seconds_Of is called with a Sub_Second value of 1.0, the value returned is equal to the value of Seconds_Of for the next second with a Sub_Second value of 0.0.
69/2
procedure Split (Seconds    : in Day_Duration;
                 Hour       : out Hour_Number;
                 Minute     : out Minute_Number;
                 Second     : out Second_Number;
                 Sub_Second : out Second_Duration);
70/3
Splits Seconds into Hour, Minute, Second and Sub_Second in such a way that the resulting values all belong to their respective subtypes. The value returned in the Sub_Second parameter is always less than 1.0. If Seconds = 86400.0, Split propagates Time_Error.
71/2
function Time_Of (Year       : Year_Number;
                  Month      : Month_Number;
                  Day        : Day_Number;
                  Hour       : Hour_Number;
                  Minute     : Minute_Number;
                  Second     : Second_Number;
                  Sub_Second : Second_Duration := 0.0;
                  Leap_Second: Boolean := False;
                  Time_Zone  : Time_Zones.Time_Offset := 0)
                          return Time;
72/2
If Leap_Second is False, returns a Time built from the date and time values, relative to the specified time zone offset. If Leap_Second is True, returns the Time that represents the time within the leap second that is one second later than the time specified by the other parameters. Time_Error is raised if the parameters do not form a proper date or time. If Time_Of is called with a Sub_Second value of 1.0, the value returned is equal to the value of Time_Of for the next second with a Sub_Second value of 0.0. 
73/2
function Time_Of (Year       : Year_Number;
                  Month      : Month_Number;
                  Day        : Day_Number;
                  Seconds    : Day_Duration := 0.0;
                  Leap_Second: Boolean := False;
                  Time_Zone  : Time_Zones.Time_Offset := 0)
                          return Time;
74/2
If Leap_Second is False, returns a Time built from the date and time values, relative to the specified time zone offset. If Leap_Second is True, returns the Time that represents the time within the leap second that is one second later than the time specified by the other parameters. Time_Error is raised if the parameters do not form a proper date or time. If Time_Of is called with a Seconds value of 86_400.0, the value returned is equal to the value of Time_Of for the next day with a Seconds value of 0.0.
75/2
procedure Split (Date       : in Time;
                 Year       : out Year_Number;
                 Month      : out Month_Number;
                 Day        : out Day_Number;
                 Hour       : out Hour_Number;
                 Minute     : out Minute_Number;
                 Second     : out Second_Number;
                 Sub_Second : out Second_Duration;
                 Leap_Second: out Boolean;
                 Time_Zone  : in Time_Zones.Time_Offset := 0);
76/2
If Date does not represent a time within a leap second, splits Date into its constituent parts (Year, Month, Day, Hour, Minute, Second, Sub_Second), relative to the specified time zone offset, and sets Leap_Second to False. If Date represents a time within a leap second, set the constituent parts to values corresponding to a time one second earlier than that given by Date, relative to the specified time zone offset, and sets Leap_Seconds to True. The value returned in the Sub_Second parameter is always less than 1.0.
77/2
procedure Split (Date       : in Time;
                 Year       : out Year_Number;
                 Month      : out Month_Number;
                 Day        : out Day_Number;
                 Hour       : out Hour_Number;
                 Minute     : out Minute_Number;
                 Second     : out Second_Number;
                 Sub_Second : out Second_Duration;
                 Time_Zone  : in Time_Zones.Time_Offset := 0);
78/2
Splits Date into its constituent parts (Year, Month, Day, Hour, Minute, Second, Sub_Second), relative to the specified time zone offset. The value returned in the Sub_Second parameter is always less than 1.0.
79/2
procedure Split (Date       : in Time;
                 Year       : out Year_Number;
                 Month      : out Month_Number;
                 Day        : out Day_Number;
                 Seconds    : out Day_Duration;
                 Leap_Second: out Boolean;
                 Time_Zone  : in Time_Zones.Time_Offset := 0);
80/2
If Date does not represent a time within a leap second, splits Date into its constituent parts (Year, Month, Day, Seconds), relative to the specified time zone offset, and sets Leap_Second to False. If Date represents a time within a leap second, set the constituent parts to values corresponding to a time one second earlier than that given by Date, relative to the specified time zone offset, and sets Leap_Seconds to True. The value returned in the Seconds parameter is always less than 86_400.0.
81/2
function Image (Date : Time;
                Include_Time_Fraction : Boolean := False;
                Time_Zone  : Time_Zones.Time_Offset := 0) return String;
82/2
Returns a string form of the Date relative to the given Time_Zone. The format is "Year-Month-Day Hour:Minute:Second", where the Year is a 4-digit value, and all others are 2-digit values, of the functions defined in Calendar and Calendar.Formatting, including a leading zero, if needed. The separators between the values are a minus, another minus, a colon, and a single space between the Day and Hour. If Include_Time_Fraction is True, the integer part of Sub_Seconds*100 is suffixed to the string as a point followed by a 2-digit value. 
83/2
function Value (Date : String;
                Time_Zone  : Time_Zones.Time_Offset := 0) return Time;
84/2
Returns a Time value for the image given as Date, relative to the given time zone. Constraint_Error is raised if the string is not formatted as described for Image, or the function cannot interpret the given string as a Time value.
85/2
function Image (Elapsed_Time : Duration;
                Include_Time_Fraction : Boolean := False) return String;
86/2
Returns a string form of the Elapsed_Time. The format is "Hour:Minute:Second", where all values are 2-digit values, including a leading zero, if needed. The separators between the values are colons. If Include_Time_Fraction is True, the integer part of Sub_Seconds*100 is suffixed to the string as a point followed by a 2-digit value. If Elapsed_Time < 0.0, the result is Image (abs Elapsed_Time, Include_Time_Fraction) prefixed with a minus sign. If abs Elapsed_Time represents 100 hours or more, the result is implementation-defined. 
87/2
function Value (Elapsed_Time : String) return Duration;
88/2
Returns a Duration value for the image given as Elapsed_Time. Constraint_Error is raised if the string is not formatted as described for Image, or the function cannot interpret the given string as a Duration value. 

Implementation Advice

89/2
 An implementation should support leap seconds if the target system supports them. If leap seconds are not supported, Difference should return zero for Leap_Seconds, Split should return False for Leap_Second, and Time_Of should raise Time_Error if Leap_Second is True. 
NOTES
90/2
38  The implementation-defined time zone of package Calendar may, but need not, be the local time zone. UTC_Time_Offset always returns the difference relative to the implementation-defined time zone of package Calendar. If UTC_Time_Offset does not raise Unknown_Zone_Error, UTC time can be safely calculated (within the accuracy of the underlying time-base).
91/2
39  Calling Split on the results of subtracting Duration(UTC_Time_Offset*60) from Clock provides the components (hours, minutes, and so on) of the UTC time. In the United States, for example, UTC_Time_Offset will generally be negative. 

Contents   Index   References   Search   Previous   Next 
Ada-Europe Ada 2005 and 2012 Editions sponsored in part by Ada-Europe