Some important NSDate extensions

NSDateExtensions.swift

extension NSDate: Comparable {}

public func < (lhs: NSDate, rhs: NSDate) -> Bool {
    return lhs.compare(rhs) == .OrderedAscending
}

// Gets you NSDate + NSTimeInterval, NSDate - NSTimeInterval, and NSDate - NSDate.
extension NSDate: Strideable {
    public func advancedBy(n: NSTimeInterval) -> Self {
        return dateByAddingTimeInterval(n)
    }
    
    public func distanceTo(other: NSDate) -> NSTimeInterval {
        return other.timeIntervalSinceDate(self)
    }
}