NSDate time converting from 12hr to 24 hr format

问题:

hi i have problem while converting Date Formats... the date time is in the Format 12 hour Format like 12/9/2010 4:00:00 PM (Month/date/year Hour:Min:sec Pm) i need to Convert it into 24 hour format like 12/9/2010 16:00:00
Can any one Help me please.... Thx in advance

回答1:

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
dateformatter.dateFormat = @"hh:mm a";
NSDate *date = [dateformatter dateFromString:departTime];
dateformatter.dateFormat = @"HH:mm";
NSString *time24 = [dateformatter stringFromDate:date];
departTimelbl.text=time24;

回答2:

Simply do This to get 24 hour time format (In Swift 2)

let formatter = NSDateFormatter()
formatter.dateFormat = "HH:mm a"  //(hh:mm a----> for 12 hour format)
let timeString = formatter.stringFromDate(NSDate())
print(timeString)

UPDATE: Swift 3 version

let formatter = DateFormatter()
formatter.dateFormat = "HH:mm a"  //(hh:mm a----> for 12 hour format)
let timeString = formatter.string(from: Date())
print(timeString)

回答3:

You need to use a NSDateFormatter. I encourage you to read the class reference as linked by Kay.

Here's how you'd do it. I'm assuming the date is originating as a NSString.

NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:@"MM-dd-yyyy HH:mm:ss"];
NSDate *myDate = [df dateFromString:yourNSString]; 
NSString *myNewDate = [formatter stringFromDate:myDate];
[formatter release];
[myDate release];

回答4:

Use these functions,this will change the date string from 12 to 24 hr formate and 24 to 12hr formate.

-(NSString *)changeformate_string24hr:(NSString *)date
{

    NSDateFormatter* df = [[NSDateFormatter alloc]init];

    [df setTimeZone:[NSTimeZone systemTimeZone]];

    [df setDateFormat:@"MM/dd/yyyy hh:mm:ss a"];

    NSDate* wakeTime = [df dateFromString:date];

    [df setDateFormat:@"MM/dd/yyyy HH:mm:ss"];


    return [df stringFromDate:wakeTime];

}

-(NSString *)changeformate_string12hr:(NSString *)date
{

    NSDateFormatter* df = [[NSDateFormatter alloc]init];

    [df setTimeZone:[NSTimeZone systemTimeZone]];

    [df setDateFormat:@"MM/dd/yyyy HH:mm:ss"];
    NSDate* wakeTime = [df dateFromString:date];


    [df setDateFormat:@"MM/dd/yyyy hh:mm:ss a"];


    return [df stringFromDate:wakeTime];

}

回答5:

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
dateFormatter.dateFormat = @"HH:mm";
NSDate *date = [dateFormatter dateFromString:@"15:15"];

dateFormatter.dateFormat = @"hh:mm a";
NSString *pmamDateString = [dateFormatter stringFromDate:date];

回答6:

Take a look at NSDateFormatter class reference and the data formatting guide. There you will find more especially the method dateFromString and stringFromDate are interesting for you. There is another question dealing with similar problem From string with locale to date on iphone sdk where you can find some sample code when you want to set a special formatting template string.

回答7:

1. In Swift

   var dateFormatter = DateFormatter()
   dateFormatter.dateFormat = "MM/dd/yyyy hh:mm:ss a"
   var date: Date? = dateFormatter.date(from: "12/9/2010 4:00:00 PM")
   dateFormatter.dateFormat = "MM/dd/yyyy HH:mm:ss"
   var convertedString: String? = nil
   if let aDate = date {
       convertedString = dateFormatter.string(from: aDate)
   }
   

2. In Objective C

   NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
   dateFormatter.dateFormat = @"MM/dd/yyyy hh:mm:ss a";
   NSDate *date = [dateFormatter dateFromString:@"12/9/2010 4:00:00 PM"];
   dateFormatter.dateFormat = @"MM/dd/yyyy HH:mm:ss";
   NSString *convertedString = [dateFormatter stringFromDate:date];