从dateFromString方法从NSDateFormatter获取错误的日期？

Question

I am trying to get NSDate object from string . I use the fallowing code

NSString *st1=@"4:39 AM";
NSDateFormatter *dateFormatter=[[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"hh:mm a"];
NSDate *dateobj=[dateFormatter dateFromString:st1];
NSLog(@"Date from string 4:39 AM is %@",dateobj);

But it gives wrong output such like as

Date from string 4:39 AM is 1969-12-31 23:09:00 +0000

What is the exact way to get the NSDate object from this type of strings.

Answer 1

Dont base your result on NSLoging NSDate , since logging it will give you the time in GMT Please refer to my answer on this question NSDateFormatter giving me time 4 hours ahead

For example if you want to fire a UILocalNotification at 4:39 am you would do the following

NSCalendar* myCalendar = [NSCalendar currentCalendar];
NSDateComponents* components = [myCalendar components:NSYearCalendarUnit|NSMonthCalendarUnit|NSDayCalendarUnit 
                                             fromDate:[NSDate date]];
//4:39 Am
[components setHour: 4]; //4 am
[components setMinute: 39];//39 minutes
[components setSecond: 0];// 0 seconds
NSDate *myDate = [myCalendar dateFromComponents:components];

NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:@"MMMM dd, yyyy h:mma"];  
NSString *str = [formatter stringFromDate:myDate];

NSLog(@"date is %@", myDate); //This will log the correct data but in GMT time zone
NSLog(@"date is %@", str); //This will log the correct data

UILocalNotification *notification = [[UILocalNotification alloc] init];
notification.fireDate = myDate;

Answer 2

This is correct. You did specify only time and not date. This way, date is assumed to be the beginning of computer age 1970/1/1 (computer zero time). NSLog then shows it depending on your time zone (GMT-5).

If you want a better answer, you have to specify what output you want. The code is correct ant the result is correct, too.