I've been looking at calendar issues in Ada, I'm trying to write a
complete calendar package for Ada. I'm trying to understand how
daylight savings works in Ada.Calendar.
An average day has 86_400 seconds (24 * 3600). However, the day where
daylight savings time is activated would seem to have 82_800 seconds (23
* 3600) and the day where daylight savings time is deactivated, as just
happened in the US, would seem to have 90_000 seconds (25 * 3600).
I would seem to me that the seconds in the day would not be dependent on
daylight savings, but would instead range 0 .. 90_000. Otherwise,
certain times cannot be represented properly in certain circumstances.
For instance, if you do the following:
with Ada.Text_IO; use Ada.Text_IO;
with Ada.Calendar; use Ada.Calendar;
procedure T1 is
Time1 : Time;
Time2 : Time;
Year1 : Year_Number;
Month1 : Month_Number;
Day1 : Day_Number;
Seconds : Duration;
Time1 := Time_Of(2001, 10, 28, 3600.0 * 1.5) + 3600.0;
Split(Time1, Year1, Month1, Day1, Seconds);
Time2 := Time_Of(Year1, Month1, Day1, Seconds);
if (Time1 = Time2) then
Put_Line("Times are equal");
Put_Line("Times are unequal");
The times will not be equal (at least on GNAT-3.12p in a US timezone).
Is this the intent? If so, there is no easy way to tell the two
"1:30AM" times apart from each other, because the calendar package gives
no way to tell if DST is active. I guess you could figure out of DST
might active on that day and add an hour to see if you get the same
"seconds" value back, but that's kind of a pain. I guess I'm used to
the Java calendar package, which is quite powerful and comples. The
whole date/time things is a big mess, anyway.
Thanks for any insight on this.