NSDate - Convert Date to GMT

Question

I need the ability to convert an NSDate value to a GMT Date.

How can I go about converting an NSDate value to a GMT formatted NSDate<

Answer 1

Swift 4:

//UTC or GMT ⟺ Local 

extension Date {

    // Convert local time to UTC (or GMT)
    func toGlobalTime() -> Date {
        let timezone = TimeZone.current
        let seconds = -TimeInterval(timezone.secondsFromGMT(for: self))
        return Date(timeInterval: seconds, since: self)
    }

    // Convert UTC (or GMT) to local time
    func toLocalTime() -> Date {
        let timezone = TimeZone.current
        let seconds = TimeInterval(timezone.secondsFromGMT(for: self))
        return Date(timeInterval: seconds, since: self)
    }

}