Difference between setting NSCalendar's timezone using `localTimeZone` vs using `timeZoneWithAbbreviation` giving different values

I have configured my phone (actual device, not simulator) to be in London UK which is GMT.

When I set the timezone on a NSCalendar using localTimeZone, it gives me the time off by 1 minute and 15 seconds as compared to if I set it using [NSTimeZone timeZoneWithAbbreviation:@"GMT"]. Shouldn't both be giving me the same result if my timezone is already set to GMT?

Another thing I notice is that if I set break points, the NSDate created using localTimeZone inspected via the breakpoint is off by 1 minute and 15 seconds but the NSLog prints the correct time (Breakpoint shows: 0000-12-30 09:01:15 UTC but NSLog prints Sat Dec 30 09:00:00 0000):

But when I use [NSTimeZone timeZoneWithAbbreviation:@"GMT"], then the breakpoint shows the correct time but the NSLog prints the wrong time off by 1 minute and 15 seconds (Breakpoint shows: 0000-12-30 09:00:00 UTC but NSLog prints Sat Dec 30 08:58:45 0000):

Here's my code along with the breakpoint and NSLog output in comments next to it:

NSLog(@"Timezone: %@",[NSTimeZone localTimeZone]);//Timezone: Local Time Zone (Europe/London (GMT) offset 0)

    NSLocale *locale = [NSLocale currentLocale];
    NSCalendar *myCalendar = [NSCalendar currentCalendar];
    [myCalendar setLocale:locale];
    [myCalendar setTimeZone:[NSTimeZone localTimeZone]];
    NSLog(@"TZ: %@",myCalendar.timeZone);//TZ: Local Time Zone (Europe/London (GMT) offset 0)

    NSDateFormatter *timeFormatter = [NSDateFormatter new];
    [timeFormatter setDateFormat:@"h:mm a"];
    [timeFormatter setLocale:locale];
    [timeFormatter setTimeZone:[NSTimeZone localTimeZone]];

    NSDateComponents* dateComps = [myCalendar components:NSCalendarUnitHour|NSCalendarUnitMinute fromDate:[timeFormatter dateFromString:@"9:00 AM"]];
    NSDate *myDate1 = [myCalendar dateFromComponents:dateComps];//Breakpoint shows: 0000-12-30 09:01:15 UTC


    NSLog(@"myDate1: %@",myDate1); // myDate1: Sat Dec 30 09:00:00 0000

    //----------------Explicitly specified timeZoneWithAbbreviation GMT:


    NSCalendar *myCalendarExplicitGMT = [NSCalendar currentCalendar];
    [myCalendarExplicitGMT setLocale:locale];
    [myCalendarExplicitGMT setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@"GMT"]];
    NSLog(@"TZ: %@",myCalendarExplicitGMT.timeZone);//TZ: GMT (GMT) offset 0

    NSDateComponents* dateCompsUsingExplicitGMT = [myCalendarExplicitGMT components:NSCalendarUnitHour|NSCalendarUnitMinute fromDate:[timeFormatter dateFromString:@"9:00 AM"]];
    NSDate *myDate2 = [myCalendarExplicitGMT dateFromComponents:dateCompsUsingExplicitGMT];//Breakpoint shows: 0000-12-30 09:00:00 UTC


    NSLog(@"myDate2: %@",myDate2); // myDate2: Sat Dec 30 08:58:45 0000

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