How can I parse / create a date time stamp formatted with fractional seconds UTC timezone (ISO 8601, RFC 3339) in Swift?

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How to generate a date time stamp, using the format standards for ISO 8601 and RFC 3339?

The goal is a string that looks like this:

"2015-01-01T00:00:00.000Z"

Format:

  • year, month, day, as “XXXX-XX-XX”
  • the letter “T” as a separator
  • hour, minute, seconds, milliseconds, as “XX:XX:XX.XXX”.
  • the letter “Z” as a zone designator for zero offset, a.k.a. UTC, GMT, Zulu time.

Best case:

  • Swift source code that is simple, short, and straightforward.
  • No need to use any additional framework, subproject, cocoapod, C code, etc.

I’ve searched StackOverflow, Google, Apple, etc. and haven’t found a Swift answer to this.

The classes that seem most promising are NSDate, NSDateFormatter, NSTimeZone.

Related Q&A: How do I get an ISO 8601 date on iOS?

Here’s the best I’ve come up with so far:

var now = NSDate()
var formatter = NSDateFormatter()
formatter.dateFormat = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'"
formatter.timeZone = NSTimeZone(forSecondsFromGMT: 0)
println(formatter.stringFromDate(now))

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