You’re supposed to use combinations of gmtime/localtime and timegm/mktime. That should give you the orthogonal tools to do conversions between struct tm and time_t. For UTC/GMT: time_t t; struct tm tm; struct tm * tmp; … t = timegm(&tm); … tmp = gmtime(t); For localtime: t = mktime(&tm); … tmp = localtime(t); All tzset() does … Read more
Joda Time (as ever) makes this really easy due to the DateTimeZone.nextTransition method. For example: import org.joda.time.*; import org.joda.time.format.*; public class Test { public static void main(String[] args) { DateTimeZone zone = DateTimeZone.forID(“Europe/London”); DateTimeFormatter format = DateTimeFormat.mediumDateTime(); long current = System.currentTimeMillis(); for (int i=0; i < 100; i++) { long next = zone.nextTransition(current); if (current … Read more
I ‘m not aware of any existing implementations and I haven’t had cause to use advanced date/time features such as these as yet, so here is a clean room implementation. To enable the syntax illustrated in the question we are going to extend DateTimeZone as follows: class DateTimeZoneEx extends DateTimeZone { const MAX_DST_SHIFT = 7200; … Read more
Yes. ConvertTimeFromUtc will automatically handle daylight saving time adjustments, as long as the time zone that you are targeting uses daylight saving time. From the MSDN documentation: When performing the conversion, the ConvertTimeFromUtc method applies any adjustment rules in effect in the destinationTimeZone time zone. You should not try to add an additional hour in … Read more
As pointed out in comments, right now (March 2022) this calculation looks likely to change next year: US may not switch off of DST in the fall. Don’t forget that daylight saving time schedules change depending on country, and also are subject to change over the years: the current (as of 2013 through 2022) US … Read more
I’ve found a method which works using PHP’s DateTimezone class (PHP 5.2+) function timezoneDoesDST($tzId) { $tz = new DateTimeZone($tzId); $trans = $tz->getTransitions(); return ((count($trans) && $trans[count($trans) – 1][‘ts’] > time())); } or, if you’re running PHP 5.3+ function timezoneDoesDST($tzId) { $tz = new DateTimeZone($tzId); return count($tz->getTransitions(time())) > 0; } The getTransitions() function gives you information … Read more
import pytz from datetime import datetime, timedelta def is_dst(zonename): tz = pytz.timezone(zonename) now = pytz.utc.localize(datetime.utcnow()) return now.astimezone(tz).dst() != timedelta(0) Usage: >>> is_dst(“America/Los_Angeles”) False >>> is_dst(“America/Sao_Paulo”) True
VBA doesn’t offer functions to do that, but the Windows API does. Luckily you can use all those functionality from VBA as well. This page describes how to do it: Time Zones & Daylight Savings Time Edit: Added Code For the posterity sake, I’ve added the complete code from Guru Chip’s page, as usable in … Read more
I had a similar problem with hydrological data from a sensor. My timestamps were in UTC+1 (CET) and did not switch to daylight saving time (UTC+2, CEST). As I didn’t want my data to be one hour off (which would be the case if UTC were used) I took the %z conversion specification of strptime. … Read more
The best way to do this is simply to use TimeZoneInfo.ConvertTimeFromUtc. // you said you had these already DateTime utc = new DateTime(2014, 6, 4, 12, 34, 0); TimeZoneInfo tzi = TimeZoneInfo.FindSystemTimeZoneById(“Pacific Standard Time”); // it’s a simple one-liner DateTime pacific = TimeZoneInfo.ConvertTimeFromUtc(utc, tzi); The only catch is that the incoming DateTime value may not … Read more