iOS : Switching between 12/24 hour times from strings - ios

Question

Interesting issue thats caught me out.
I receive string times from a server to a device. which I then convert in to a NSDate.
When the device was set to displaying 24hour times, life was good.
Now I am testing it on a device set to 12hour times. everything has stopped working. Dates are coming back as null
I first had
NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
[dateFormat setDateFormat:#"HH:mm"];
self.startTime = [dateFormat dateFromString:(NSString *)self.startTime];
Worked perfectly for devices showing 24hour dates but not 12hour.
I then tried
NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
[dateFormat setDateFormat:#"hh:mm"];
self.startTime = [dateFormat dateFromString:(NSString *)self.startTime];
This works fine up until 12 noon, then all dates are returned as null
Update
I have also tried adding "a" but this still results in returning null
if (startDate == nil)
{
NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
[dateFormat setDateFormat:#"hh:mm a"];
startDate = [dateFormat dateFromString:(NSString *)self.startTime];
}
Update 2
Adding local, adding :ss adding a all still do not work
NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
NSLocale *twelveHourLocale = [[NSLocale alloc] initWithLocaleIdentifier:#"en_US_POSIX"];
dateFormat.locale = twelveHourLocale;
[dateFormat setDateFormat:#"hh:mm a"];
startDate = [dateFormat dateFromString:(NSString *)self.startTime];

Answer 1

It's close... I think you need:
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
NSLocale *locale = [[NSLocale alloc] initWithLocaleIdentifier:#"en_US_POSIX"];
[dateFormatter setLocale:locale];
[dateFormatter setDateFormat:#"HH:mm"];
startDate = [dateFormatter dateFromString:(NSString *)self.startTime];

Answer 2

You can try this
12 to 24 hour format
NSDateFormatter* df = [[NSDateFormatter alloc] init];
[df setLocale:[[NSLocale alloc] initWithLocaleIdentifier:#"en_US_POSIX"]];
[df setTimeZone:[NSTimeZone systemTimeZone]];
[df setDateFormat:#"hh:mm a"];
NSDate* newDate = [df dateFromString:LocationTrackingStartTime];
[df setDateFormat:#"HH:mm"];
newDate = [df stringFromDate:newDate];
24 to 12 hour format
NSDateFormatter* df = [[NSDateFormatter alloc] init];
[df setLocale:[[NSLocale alloc] initWithLocaleIdentifier:#"en_US"]];
[df setTimeZone:[NSTimeZone systemTimeZone]];
[df setDateFormat:#"yyyy-mm-dd hh:mm:ss"];
NSDate* newDate = [df dateFromString:[df stringFromDate:[NSDate date]]];
[df setDateFormat:#"hh:mm a"];
newDate = [df stringFromDate:[NSDate date]];

Answer 3

You have to add am/pm:
NSLocale *twelveHourLocale = [[NSLocale alloc] initWithLocaleIdentifier:#"en_US_POSIX"];
dateFormat.locale = twelveHourLocale;
[dateFormat setDateFormat:#"hh:mm: a"];

Answer 4

Change 24 hours format to 12 hour format,
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
//Set 24 hours date format
dateFormatter.dateFormat = #"HH:mm";
//Here #"your24hours date string" is your string date with 24 hours format
NSDate *date = [dateFormatter dateFromString:#"your24hours date string"];
//Set 12 hours date format
dateFormatter.dateFormat = #"hh:mm a";
NSString *strDate = [dateFormatter stringFromDate:date];
NSLog (#"%#", strDate);
//Output is in 12 hours date format.

Answer 5

You wanted to convert an NSDate forced to NSString to an NSDate again.
First you have to convert it to and NSString, not forcing it!
I also support 12 and 24 hour formats and i have no problem with it.

Answer 6

NSDateFormatter* df = [[NSDateFormatter alloc]init];
[df setLocale:[[NSLocale alloc] initWithLocaleIdentifier:#"en_US"]];
[df setTimeZone:[NSTimeZone systemTimeZone]];
[df setDateFormat:#"MM/dd/yyyy hh:mm a"];
NSDate* newDate = [df dateFromString:strDate4Convert];
[df setDateFormat:#"MM/dd/yyyy HH:mm:ss"];
NSString *newTimeStr = [df stringFromDate:newDate];

Answer 7

You just need to set the locale to take the am pm format. And everything else as usual.
NSDateFormatter * df = [[NSDateFormatter alloc]init];
NSLocale *locale = [[NSLocale alloc] initWithLocaleIdentifier:#"en_US_POSIX"];
[df setLocale:locale];
[df setDateStyle:NSDateFormatterNoStyle];
[df setTimeStyle:NSDateFormatterShortStyle];
NSLog(#"%#", [df stringFromDate:pickUpDate]);