Adding an amount of hours to NSDate isn't working? - ios

Question

I've spent a good few hours trying to make this work. Here's what I'm trying to do:
Take input from a UITextField in the form HH:mm AM/PM
Convert that string into an NSDate object, and update the month/day/year properties of that NSDate to reflect the curren month/day/year.
Add 4 hours to the time of the NSDate object.
That last bit isn't working. It works for times such as 12:00 PM and 12:30 PM but for times such as 2:30 PM, it will output 4:30 PM rather than 6:30 PM as expected. Here is my code, broken up to reflect those three tasks.
Task 1 - checking to see if the text input was HH:mm AM/PM
NSDateFormatter *format = [[NSDateFormatter alloc] init];
[format setLocale:[[NSLocale alloc] initWithLocaleIdentifier:#"en_US"]];
[format setTimeZone:[NSTimeZone systemTimeZone]];
[format setDateFormat:#"HH:mm a"];
NSString *dateString = textField.text;
NSLog(#"input datestring: %#", dateString);
NSDate *parsed = [format dateFromString:dateString];
if (parsed) {
NSLog(#"datestring is valid, %#", parsed);
}
Task 2- Updating the m/d/y components of that date to reflect today's.
//gregorian calendar, get the hour and minute components from the input time
NSCalendar *greg = [[NSCalendar alloc] initWithCalendarIdentifier:NSCalendarIdentifierGregorian];
NSDateComponents *components = [greg components: NSCalendarUnitHour | NSCalendarUnitMinute fromDate:parsed];
//get the month/day/year components from the current date
NSDateComponents *comps = [[NSCalendar currentCalendar] components:NSCalendarUnitDay | NSCalendarUnitMonth | NSCalendarUnitYear fromDate:[NSDate date]];
//set the components of the original date to the month/day/year components of today
[components setYear:comps.year];
[components setDay:comps.day];
[components setMonth:comps.month];
//create the new date.
NSDate* newDate = [greg dateFromComponents:components];
NSLog(#"########### %#", newDate);
Task 3 - Add 4 hours.
int hours = 4 ;
NSString *output;
NSDateComponents *add = [[NSDateComponents alloc] init];
[add setHour:hours];
newDate = [greg dateByAddingComponents:add toDate:newDate options:0];
NSDateFormatter *df = [[NSDateFormatter alloc] init];
[df setDateStyle:NSDateFormatterShortStyle];
[df setTimeStyle:NSDateFormatterShortStyle];
output = [df stringFromDate:newDate];
NSLog(#"new date: %#", output);
Log:
2015-08-27 16:03:35.672 Del Taco[1960:117431] input datestring: 2:30 pm
2015-08-27 16:03:35.673 Del Taco[1960:117431] datestring is valid, 2000-01-01 20:30:00 +0000
2015-08-27 16:03:35.673 Del Taco[1960:117431] ########### 2015-08-27 19:30:00 +0000
2015-08-27 16:03:35.674 Del Taco[1960:117431] new date: 8/27/15, 4:30 PM

Answer 1

I think I have this figured out. It was my date formatter where I set the format like this:
#"HH:mm a"
I went to Unicode's website to double check that I was doing this right, and ended up changing my format string to:
#"h:mm a"
And things seem to be working out well!