iOS:将 UTC NSDate 转换为本地时区 [英] iOS: Convert UTC NSDate to local Timezone

问题描述

如何在 Objective C 或/和 Swift 中将 UTC NSDate 转换为本地时区 NSDate?

How do I convert a UTC NSDate to local timezone NSDate in Objective C or/and Swift?

推荐答案

NSTimeInterval seconds; // assume this exists
NSDate* ts_utc = [NSDate dateWithTimeIntervalSince1970:seconds];

NSDateFormatter* df_utc = [[[NSDateFormatter alloc] init] autorelease];
[df_utc setTimeZone:[NSTimeZone timeZoneWithName:@"UTC"]];
[df_utc setDateFormat:@"yyyy.MM.dd G 'at' HH:mm:ss zzz"];

NSDateFormatter* df_local = [[[NSDateFormatter alloc] init] autorelease];
[df_local setTimeZone:[NSTimeZone timeZoneWithName:@"EST"]];
[df_local setDateFormat:@"yyyy.MM.dd G 'at' HH:mm:ss zzz"];

NSString* ts_utc_string = [df_utc stringFromDate:ts_utc];
NSString* ts_local_string = [df_local stringFromDate:ts_utc];

// you can also use NSDateFormatter dateFromString to go the opposite way

格式化字符串参数表:

https://waracle.com/iphone-nsdateformatter-date-formatting-table/

如果优先考虑性能，您可能需要考虑使用 strftime

If performance is a priority, you may want to consider using strftime

https:///developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man3/strftime.3.html

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