Strip the minutes and seconds from a date, keeping yymmddhh

hour_floor.swift

    /** Strip minutes and seconds from a date
    */
    func hourFloorFromDate(date: NSDate) -> NSDate? {
        let calendar: NSCalendar
        
        if let c = NSCalendar(calendarIdentifier: NSCalendarIdentifierGregorian) { calendar = c } else { return nil }
        
        let units = NSCalendarUnit.CalendarUnitYear | .CalendarUnitMonth | .CalendarUnitDay | .CalendarUnitHour
        
        return calendar.dateFromComponents(calendar.components(units, fromDate: date))
    }