UI Slider Time of Day Beyond Midnight?

Question

So this is a unique situation. I have a double slider I made using swift to make a time range picker like the one Kayak has. Unfortunately mine needs to be a time range between 00:00 all the way to 04:00 the following morning.

It was easy to get it from 00:00 to 23:59 using a scale of 86340 seconds for my slider control. I simply plug that into this little function and out pops the correct range on both ends/knobs:

func getTimeStringFromSeconds(seconds: Double) -> String {
    let dcFormatter = NSDateComponentsFormatter()
    dcFormatter.zeroFormattingBehavior = NSDateComponentsFormatterZeroFormattingBehavior.Pad
    dcFormatter.allowedUnits = [NSCalendarUnit.Hour, NSCalendarUnit.Minute]
    dcFormatter.unitsStyle = NSDateComponentsFormatterUnitsStyle.Positional
    return dcFormatter.stringFromTimeInterval(seconds)!
}

As you can see in the screenshot above though I have 100740 seconds instead as the scale. How can I get it to go beyond 23:59, then reset to 00:00 and go into the next day? I can make it go to 28:00 as seen above which would technically be 4am but I want it to start over and show 04:00, not 28:00. What's a good solution for this?

Just as a note, my only solution so far was a sort of hack to make the label say 0:00 by resetting the seconds to 0.00 once it goes over 86340. The scale is still 100740 but there's some math like the following to make the label say otherwise without messing with the value of the knob (upperValue):

if upperKnobLayer.highlighted {
            upperValue += valueDelta
            upperValue = max(min(maximumValue, upperValue), lowerValue)
            var upperDouble = Double(round(upperValue))
            if upperDouble > 86340.00 {
                let newValue = upperDouble - 86340
                upperDouble = 0.00 + newValue
            }
            upperTime = getTimeStringFromSeconds(upperDouble)
}

Answer 1

It would help to post the implementation of your picker but generally you want the sliders value type to be NSTimeIntervals. Then you can have a reference date which will be midnight 00:00 of today. You can use NSDate(timeIntervalSince:referenceDate) to then get an NSDate representing any date since that reference date which can be formatted accordingly and display to the screen. The added benefit of this way is that the actual day of the date will be correct if your timeInterval makes it spill over to the next day