A minor inconsistency was introduced in Plasma 5, which I suggest fixing mainly for aesthetical reasons: If you select the Slideshow wallpaper type,  you cannot set the Seconds to 0, even if you have Hours or Minutes to a value greater than 0. If you choose OK to exit the menu then open it again, Seconds is always reverted to 1.

I realize this was intended so you don't accidentally set the slideshow interval to nothing, which would obviously cause breakage. But the seconds field should only be reverted from 0 to 1 if the hours or minutes fields are also 0! Example: 0 hours 0 minutes 0 seconds is invalid, but 0 hours 15 minutes 0 seconds is valid, and should not be persisted as 0 hours 15 minutes 1 seconds.

Reproducible: Always

Steps to Reproduce:
1. Right click your desktop and select Desktop Settings.
2. Set the wallpaper type to Slideshow.
3. For the interval, set hours or minutes to any value greater than 0 (either just one of them or both) but leave seconds at 0.
4. Click the OK button to confirm and close the Desktop Settings window.
5. Repeat step 1 and open Desktop Settings back up.

Actual Results:  
The seconds field has now become 1.

Expected Results:  
As long as the hours or minutes fields are greater than 0, the seconds field should be left at 0.