Convert Date from one format to another - ios

Question

I trying to convert date from one format to another. But the date in the below code is coming as nil. Can you guys help me out below is the code.
func eventTimeDate() -> Date {
let dtf = DateFormatter()
dtf.timeZone = TimeZone.current
dtf.dateFormat = "yyyy-MM-dd HH:mm:ss z"
/// "2020-05-28 00:20:00 GMT+5:30"
let stringDate = dtf.string(from: self)
let dateFormatter = DateFormatter()
dateFormatter.dateFormat = "yyyy/MM/dd HH:mm:ss z"
/// nil
let date = dateFormatter.date(from: stringDate)
return date!
}

Answer 1

If you need to convert from one formatted date string to another formatted date string, you can use two DateFormatters: one - an input formatter to convert a String to an intermediary Date object, and then - using an output formatter - convert from Date to String.
func reFormat(from dateStr: String) -> String? {
let fromFormatter = DateFormatter()
fromFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss z"
let toFormatter = DateFormatter()
toFormatter.dateFormat = "yyyy/MM/dd HH:mm:ss z"
guard let date = fromFormatter.date(from: dateStr) else { return nil }
return toFormatter.string(from: date)
}
If you just need to return a Date object, then it's a simpler function using just one DateFormatter:
func toDate(from dateStr: String) -> Date? {
let formatter = DateFormatter()
formatter.dateFormat = "yyyy-MM-dd HH:mm:ss z"
return formatter.date(from: dateStr)
}
Date object itself has no formatting - it's a pure representation of a date & time, which you can convert to/from using different formatters.

Answer 2

A swift class Date has no format.
In your code your stringDate is in "yyyy-MM-dd HH:mm:ss z" format. If you need to convert String to Date you must use the same format otherwise it will return nil.
If you want to change a format of a string then first convert it to a Swift 'Date' then again convert it to a string with the use of new Formatter.
func eventTimeDate(dateString : String, currentFormat : String, newFormat : String) -> String? {
let currentDateFormatter = DateFormatter()
currentDateFormatter.calendar = Calendar(identifier: Calendar.Identifier.gregorian)
currentDateFormatter.locale = Locale(identifier: "en_IN")
currentDateFormatter.dateFormat = currentFormat
let date = currentDateFormatter.date(from: dateString)
let newDateFormatter = DateFormatter()
newDateFormatter.calendar = Calendar(identifier: Calendar.Identifier.gregorian)
newDateFormatter.locale = Locale(identifier: "en_IN")
newDateFormatter.dateFormat = newFormat
if let date = date {
let newDateString = newDateFormatter.string(from: date)
return newDateString
}
return nil
}

Answer 3

You have three problems in your code. First when parsing a fixed date format you should always set the date formatter's locale to "en_US_POSIX". Second you need to escape the GMT of your date string. Last but not least important you need to fix your timezone string which it is missing the leading zero for your timezone hour:
let dateStr = "2020-05-28 00:20:00 GMT+5:30"
let formatter = DateFormatter()
// set the date formatter's locale to "en_US_POSIX"
formatter.locale = .init(identifier: "en_US_POSIX")
// escape the GMT of your date string
formatter.dateFormat = "yyyy-MM-dd HH:mm:ss 'GMT'Z"
// add the leading zero for your timezone hour
let string = dateStr.replacingOccurrences(of: "(GMT[+-])(\\d:)", with: "$10$2", options: .regularExpression)
if let date = formatter.date(from: string) {
print(date) // "2020-05-27 18:50:00 +0000\n"
}