I had some support tickets about dates not showing properly for customers based in the America/Merida timezone.
Essentially America/Merida permanently changed to -0500 (CDT) on October 31, 2021, and it appears that the NSTimeZone does not respect this change, and reports times as -0600 (CST).
Creating a little test tool with the following code:
+(void) run {
NSArray<NSString *> * args = [[NSProcessInfo processInfo] arguments];
if ([args count] > 1) {
NSString *timezone = args[1];
NSLog(@"custom TZ: %@", timezone);
NSTimeZone * tz = [NSTimeZone timeZoneWithName:timezone];
[NSTimeZone setDefaultTimeZone:tz];
}
NSDate * now = [NSDate date];
NSLog(@"Testing Dates: (local timezone : %@)", [NSTimeZone localTimeZone]);
NSLog(@" (default timezone: %@)", [NSTimeZone defaultTimeZone]);
NSLog(@" (is DST : %@)", [[NSTimeZone defaultTimeZone] isDaylightSavingTimeForDate:now] ? @"YES" : @"NO");
NSLog(@" (current cal-tz : %@)", [[NSCalendar currentCalendar] timeZone]);
NSLog(@" (current locale : %@)", [[NSLocale currentLocale] localeIdentifier]);
NSLog(@"Now: %@", now);
}
And running with the America/Merida timezone passed in, I'm getting the following output:
custom TZ: America/Merida
Testing Dates: (local timezone : Local Time Zone (America/New_York (EDT) offset -14400 (Daylight)))
(default timezone: America/Merida (CST) offset -21600)
(is DST : NO)
(current cal-tz : America/Merida (CST) offset -21600)
(current locale : en_US)
Now: Tue May 14 15:06:14 2024
Running the same code on Linux via the GNUStep implementation of Objective-C, I get the correct output with America/Merida showing up as CDT (ie (is DST : YES)).
Are there any good ways to work around this?
Consider this:
import Foundation
func main() {
var c = Calendar(identifier: .gregorian)
c.timeZone = .gmt
let jan2022 = c.date(from: .init(year: 2022, month: 1, day: 1))!
let jun2022 = c.date(from: .init(year: 2022, month: 6, day: 1))!
let jan2023 = c.date(from: .init(year: 2023, month: 1, day: 1))!
let jun2023 = c.date(from: .init(year: 2023, month: 6, day: 1))!
let tz = TimeZone(identifier: "America/Merida")!
for d in [jan2022, jun2022, jan2023, jun2023] {
print(tz.isDaylightSavingTime(for: d), tz.daylightSavingTimeOffset(for: d), tz.secondsFromGMT(for: d) / 60 / 60)
}
}
main()
On macOS 14.4.1 it prints:
false 0.0 -6
true 3600.0 -5
false 0.0 -6
false 0.0 -6
That definitely matches your assertion that this time zone is ‘stuck’ on standard time rather than daylight savings time.
However, I’m confused by this assertion:
Essentially
America/Meridapermanently changed to -0500 (CDT) on October 31, 2021
The Wikipedia summary of Mexican time zones suggests that America/Merida is effectively deprecated in favour of America/Mexico_City. And if I plug America/Mexico_City into the above code, it prints the same results.
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Quinn “The Eskimo!” @ Developer Technical Support @ Apple
let myEmail = "eskimo" + "1" + "@" + "apple.com"
