Using DateFormatter to parse this string into a Date? - ios

Question

I'm hitting a webservice that is returning a string in the following format:
"yyyy-MM-dd'T'HH:mmZ"
It's very close to the standard UTC format, but just without the ss at the end. My issue is that my dateFormatter is always returning nil...and I have tried to make sure that locale and everything else is setup properly.
Here is an example of an actual string:
2019-12-26T00:00Z
Here is the code that creates the DF:
extension DateFormatter {
#objc static func defaultDateFormat(_ format: String) -> DateFormatter {
let formatter = DateFormatter()
formatter.locale = Locale(identifier: "US")
formatter.dateFormat = format
return formatter
}
func date(from string: String?) -> Date? {
if let string = string {
return self.date(from: string)
} else {
return nil
}
}
func string(fromOptional date: Date?) -> String? {
if let date = date {
return self.string(from: date)
} else {
return nil
}
}
func string(fromOptional date: Date?, defaultStr: String) -> String {
return self.string(fromOptional: date) ?? defaultStr
}
}
let df = DateFormatter.defaultDateFormat("yyyy-MM-dd'T'HH:mmZ")
let date: Date? = df.date(from: __dateString__) // always nil

Answer 1

A few observations:
You want to use a locale of en_US_POSIX, an invariant locale that always works for ISO 8601 / RFC 3339 date strings. See Technical Q&A 1480.
If you want to use this formatter to convert a date back to a string like 2019-12-26T00:00Z, you will want to:
Use X (or ZZZZZ or XXXXX) in your format string, not Z (see the “zone” section in the table at Date Format Patterns and you’ll see how these various time zone patterns, e.g. Z, ZZZZZ, and X, are interpreted); and
Set the timeZone of the formatter to use Zulu/GMT/UTC.
Thus:
#objc static func defaultDateFormat(_ format: String) -> DateFormatter {
let formatter = DateFormatter()
formatter.locale = Locale(identifier: "en_US_POSIX")
formatter.timeZone = TimeZone(secondsFromGMT: 0)
formatter.dateFormat = format
return formatter
}
And
let df = DateFormatter.defaultDateFormat("yyyy-MM-dd'T'HH:mmX")
let date = df.date(from: "2019-12-26T00:00Z")
Or
let string = df.string(from: Date())