Wednesday, March 12, 2014
For now, until this can be automated
One of the tasks I do at work every day is to pull the latest updates of the several source repositories I have checked out and view the changes. It keeps me up to date. One particular change caught my eye:
r4245 | XXXXXXX | 2014-03-12 11:36:38 -0400 (Wed, 12 Mar 2014) | 1 line
update for Daylight Savings Time
Really?
We have networked computers, running the latest operating systems, and we're still manually updating the time zone? (Okay, to be fair, this is code to test code, but still …)
Now granted, getting the time zone information in a portable manner is not always that easy. In C, there is no direct way to obtain the timezone, and thus, you need to do something like:
time_t now; struct tm slocal; struct tm sgmt; time_t local; time_t gmt; double zone; now = time(NULL); slocal = *localtime(&now); sgmt = *gmtime(&now); local = mktime(&slocal); gmt = mktime(&sgmt); zone = difftime(local,gmt);
zone is the number of seconds from UT; divide by 3,600 to get the time zone
(well, the quotient is the timezone, the remainder needs to be multiplied by
3,600 then divided by 60 to get the minutes).
And that's just to be “portable”—POSIX (read: most
modern Unix systems these days) include a way to obtain the timezone more
directly, just call tzset() and the global variables
extern char *tzname[2] and extern long timezone
are initialized.
You don't need to hardcode a timezone.
But I was curious, and I checked the log for the file in question:
r4245 | XXXXXXX | 2014-03-12 11:36:38 -0400 (Wed, 12 Mar 2014) | 1 line update for Daylight Savings Time ------------------------------------------------------------------------ r3889 | XXXXXXX | 2013-11-04 13:21:02 -0500 (Mon, 04 Nov 2013) | 1 line Support for XXXXXXXX. Changed the Manual UTC offset constant to reflect DST change. Ran a couple tests and they were all passing after making the change. ------------------------------------------------------------------------ r3245 | XXXXXXX | 2013-03-07 15:20:00 -0500 (Thu, 07 Mar 2013) | 1 line Fixing utc offset for day-light savings shift. ------------------------------------------------------------------------ r2923 | XXXXXXX | 2012-11-05 11:30:04 -0500 (Mon, 05 Nov 2012) | 1 line Adjust time offset value for daylight savings. ------------------------------------------------------------------------ r1827 | XXXXXXX | 2012-03-12 12:08:41 -0400 (Mon, 12 Mar 2012) | 1 line Update for daylight savings time. ------------------------------------------------------------------------ r1154 | XXXXXXX | 2011-11-14 19:28:32 -0500 (Mon, 14 Nov 2011) | 1 line Remove unneeded constants. ------------------------------------------------------------------------ r1091 | XXXXXXX | 2011-11-04 19:32:51 -0400 (Fri, 04 Nov 2011) | 1 line Adjusting UTC_OFFSET for day light savings.
And the punchline? The comment above the timezone constant:
// UTC Offset (for now until this can be automated)
which was added in April of 2011.
