how to save daily reward timer by playerprefs ?

Hi guys. ((( I have seen all scripts about this subject all over the net. But those script dont work for me.)))

I want making daily count down timer with get reward button for my android game. If timer recive to (0:0) timer stop and ,get reward button setactive true and player can add coins to all score text. Then get reward button setactive false and timer run again to another day. I want using playerprefs to save timer Please help me Thanks a lot