How to calculate how much time passed from the date with timezone?

I get from the server a date with this format:

2016-05-27 17:33:43+0400

Now, I want to detect, how much time passed since that date? For example 1 day 5 hours 10 minutes 20 seconds.

How can I do it? I know how to calculate this from the timestamp, but do not know how to convert this to a timestamp.

Can anyone help me with it?

For example:

Convert this 2016-05-27 17:33:43+0400 to 1464370423 this

Or maybe there are another solution. I just want to calculate how much time passed since that time

Solution

You can use NSDateComponents formatter to get the relative time between two dates. Regarding the date string format you need to use xx for the time zone part.

let dateStr = "2016-05-27 17:33:43+0400"

let formatter = NSDateFormatter()
formatter.dateFormat = "yyyy-MM-dd HH:mm:ssxx"
formatter.calendar = NSCalendar(calendarIdentifier: NSCalendarIdentifierISO8601)
formatter.locale = NSLocale(localeIdentifier: "en_US_POSIX")
if let date = formatter.dateFromString(dateStr) {
    print(date)   // "2016-05-27 13:33:00 +0000\n" -4hs
    let dateComponentsFormatter = NSDateComponentsFormatter()
    dateComponentsFormatter.allowedUnits = [.Day,.Hour,.Minute,.Second]
    dateComponentsFormatter.unitsStyle = .Full
    print(dateComponentsFormatter.stringFromDate(date, toDate: NSDate()) ?? "") // 6 days, 17 hours, 51 minutes, 29 seconds
}