unexpected result of dateFromComponents:

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清酒与你
清酒与你 2021-01-21 11:51

the following code

NSCalendar *cal = [NSCalendar currentCalendar];
[cal setFirstWeekday:2];
[cal setMinimumDaysInFirstWeek:4];

NSDateComponents *comp = [[NSDate         


        
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  • 2021-01-21 12:19

    I assume you are using the CET time zone locally. This is what the [NSCalendar currentCalendar] will use as a time zone then.

    When you dump a NSDate with NSLog, you will get the date in its raw UTC form. To print the date using a local format, look into the NSDateFormatter class, which has a timeZone property:

    ....
    NSDate *date = [cal dateFromComponents:comp];
    NSDateFormatter* fmt = [[NSDateFormatter alloc] init];
    fmt.timeZone = [NSTimeZone defaultTimeZone]; // Probably not required
    NSLog(@"date:%@", [fmt stringFromDate:date]);
    
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  • 2021-01-21 12:29

    set timezone

    NSCalendar *cal = [NSCalendar currentCalendar];
    
    [cal setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@"GMT"]];
    
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  • 2021-01-21 12:33

    When you call dateFromComponents: you lose all of the timezone and calendar information and are left an NSDate object that contains the moment in time your date components represent, but nothing else. When you use NSLog on your NSDate object, that moment in time is converted to a time in UTC and rendered as a human readable string.

    You need to provide more info about what you're trying to achieve to be able to answer your second question of how to avoid this.

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