Get only time from Date - ios

Question

How to get only time from the date with am/pm. Below is my code what I have tried so far:
func changeFormat(str:String) -> String {
let dateFormatter = DateFormatter()
let newDateFormatter = DateFormatter()
// step 1
dateFormatter.dateFormat = "MM/dd/yyyy HH:mm aa" // input format
newDateFormatter.dateFormat = "HH:mm aa" // output format
let date = dateFormatter.date(from: str)!
// step 2
let string = newDateFormatter.string(from: date)
return string
}
Usage:
let strTimeFromDate = changeFormat(str: self.response?.Data[indexPath.row].ADateTime ?? "")
input date:
06/22/2021 2:00 PM
output:
12:45 PM
Getting wrong time return after formatting. Please guide what's wrong with above code

Answer 1

As mentioned by #JoakimDanielson in the comment, you are mixing HH (24 hours format) with hh (12 hours format). Using hh for the dateFormatter (given your input has 02:00 PM) should fix your issue (as long as this input value was captured in the same time zone in which you intend to convert).
In case you are still seeing that the output is not expected, then it is the issue with missing timeZone info in your input. You are trying to convert String > Date > String without specifying an input timeZone & output timeZone. You can try printing these values in your implementation.
print("dateFormatter.timeZone.secondsFromGMT() : \(dateFormatter.timeZone.secondsFromGMT())")
let date = dateFormatter.date(from: str)!
print("parsed date : \(date)")
print("\n ------------------------ \n")
// step 2
print("newDateFormatter.timeZone.secondsFromGMT() : \(newDateFormatter.timeZone.secondsFromGMT())")
let string = newDateFormatter.string(from: date)
print("parsed string : \(string)")
For me it prints following. 19800 / (60 * 60) = 5.5 (+05:30)
dateFormatter.timeZone.secondsFromGMT() : 19800
parsed date : 2021-06-22 06:30:00 +0000
------------------------
newDateFormatter.timeZone.secondsFromGMT() : 19800
parsed string : 12:00 PM
The issue is - for these two conversions to happen correctly - you must specify an appropriate time zone.
String to Date
Date to String
Here's what that implementation could look like. Assuming input is "06/22/2021 2:00 PM +0530"
func changeFormat(str: String) -> String {
let dateFormatter = DateFormatter()
dateFormatter.timeZone = TimeZone(secondsFromGMT: Int(5.5*60*60)) // +05:30
let newDateFormatter = DateFormatter()
newDateFormatter.timeZone = TimeZone(secondsFromGMT: Int(5.5*60*60)) // +05:30
dateFormatter.dateFormat = "MM/dd/yyyy hh:mm aa Z"
newDateFormatter.dateFormat = "hh:mm aa"
let date = dateFormatter.date(from: str)!
let string = newDateFormatter.string(from: date)
return string
}
When you are consuming this date string from your backend server, you should consider using appropriate time zone for it. An example, assuming input is "06/22/2021 2:00 PM +0000" -
func changeFormat(str: String) -> String {
let dateFormatter = DateFormatter()
dateFormatter.timeZone = TimeZone(secondsFromGMT: 0) // Server timeZone (UTC)
let newDateFormatter = DateFormatter()
newDateFormatter.timeZone = TimeZone.current // User's timeZone
dateFormatter.dateFormat = "MM/dd/yyyy hh:mm aa Z"
newDateFormatter.dateFormat = "hh:mm aa"
let date = dateFormatter.date(from: str)!
let string = newDateFormatter.string(from: date)
return string
}

Answer 2

"HH" is for 24h format and "aa" is for 12h format so you can't mix them, so you should use "hh:mm a" instead for both DateTimeFormatter's