Convert from just the hours:minutes:timezone to a complete date in another TimeZone

Question

I am retrieving some dates from a remote server. Unfortunately one of the possible formats is just h:mm:a

Example of data I downloaded yesterday May, 21, 2013:

1) 04:36PM EDT

2) 11:51PM EDT

The data server TimeZone is "America/New_York".

My data TimeZone is "Europe/Rome".

This is the code I've written and until this morning at 5am I thought it worked:

NSDate *myDate = @"04:36PM EDT"; //11:51PM EDT (I know the date is May, 21 2013 but it is not in the data!)

NSArray *component = [mydate componentsSeparatedByString:@" "];

//Remove any reference to the TimeZone
//set it in the dateFormatter

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
dateFormatter.dateFormat =@"MM dd yyyy h:mma";
dateFormatter.locale = [[NSLocale alloc] initWithLocaleIdentifier:@"en_US"];
dateFormatter.timeZone = [[NSTimeZone alloc] initWithName:@"America/New_York"];

//Create a valid date for the hour

NSDate *date = [NSDate date];
NSCalendar *calendar = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDateComponents *dateComponents = [calendar components:(NSYearCalendarUnit | NSMonthCalendarUnit | NSDayCalendarUnit) fromDate:date];

NSDate *dateObject = [self.dateFormatter dateFromString: [NSString stringWithFormat:@"%u %u %u %@",
                dateComponents.month,
                dateComponents.day,
                dateComponents.year,
                [component objectAtIndex:0]]];

//Convert to local timeZone             

dateFormatter.timeZone = [NSTimeZone localTimeZone]; //  @"Europe/Rome"
dateFormatter.dateStyle = NSDateFormatterShortStyle;
dateFormatter.timeStyle = NSDateFormatterLongStyle;


NSString *localTimeZoneDate = dateFormatter stringFromDate:[dateObject];

NSLog(@"Local Time Zone Date = %@", localTimeZoneDate);

Output

While yesterday the code seemed to work fine because when I made the tests I still was in the 6 hour timespan that kept me in the same day, the May 21, this morning I found it doesn't. The problem is in the creation of the right date.

1) 04:36PM EDT ----> 22/05/2013 22:36:00 CEST

The correct output should have been 21/05/2013 22:36 CEST

2) 11:51PM EDT ----> 23/05/2013 05:51:00 CEST

The correct output should have been 22/05/2013 05:51 CEST

What would be the best code to handle this special case?

Thanks

Nicola

Answer 1

For now I am doing this: I look if the recreated date in local time is in the future in respect to the current hour local time. If yes it should be enough to remove one or more days from the recreated date.

Answer 2

Try

NSString *dateString = @"04:36PM EDT"; //11:51PM EDT (I know the date is May, 21 2013 but it is not in the data!)

NSArray *component = [dateString componentsSeparatedByString:@" "];

//Remove any reference to the TimeZone
//set it in the dateFormatter

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
dateFormatter.dateFormat =@"MM dd yyyy";
dateFormatter.locale = [[NSLocale alloc] initWithLocaleIdentifier:@"en_US"];
dateFormatter.timeZone = [[NSTimeZone alloc] initWithName:@"America/New_York"];

NSString *tempDateString = [dateFormatter stringFromDate:[NSDate date]];
dateString = [tempDateString stringByAppendingFormat:@" %@",component[0]];

dateFormatter.dateFormat =@"MM dd yyyy hh:mma";
NSDate *tempDate = [dateFormatter dateFromString:dateString];

dateFormatter.timeZone = [NSTimeZone localTimeZone]; 
dateFormatter.dateStyle = NSDateFormatterShortStyle;
dateFormatter.timeStyle = NSDateFormatterLongStyle;

NSString *localDateString = [dateFormatter stringFromDate:tempDate];

NSLog(@"Local Time Zone Date = %@", localDateString);

Answer 3

I haven't checked this yet, but I think it is because the calendar you create is for yuor time zone. Try setting the calendar timezone to America/New York before getting the date components out.