Can I do the same for building parts? Like... I want buildings take damage %50 less at 1am ...

That would be very complicated for the config.  I am looking at cleaning up the config.  Time multiplier across building components is probably too long to maintain, doing it across all building would not be too bad.

Yea, actually that would be easier and that is what I'm looking for. Damage Control only for building. If you can code a simple plugin for me just for that, i can test it.

Added to Damage control so you can have safe hours for building and unsafe ones.  Note that if the other multiplers for building are zero they take no damage.  So if you plan to allow raiding you will need to adjust them accordingly.

You might want to look at these plugins as well, as some of them are simpler to work with:
https://umod.org/plugins?page=1&sortdir=asc&query=damage

"Building_Time_Multipliers": { " 0": 0.5, .... So If I make it like this, 0.5 btw 0-1 am , building parts will take %50 less damage right? But it did not work.

Correct it is a multipler so 0.5 = half damage, 0 = no damage, 1 = normal damage and 2 = double damage.

But the other multiplers apply too.  So if you set a multipler to zero then the time multipler does nothing net.  all multiplers are cummlative.

I did not set any multipler of building part to 0. They are default. I only change  building time and it did not work. How do I disable other multiplers and work only with building_time then?

shoot me your config I will check it.