It kinda easy...haha. But it really depends on how far you want to go. but i'll try to help. So first of all, i sugest that this be in a common event, it wouldbe dumb not to put it in there. Ok so here we go. so you need some Var.s!! One for Sec.s, Min.s, Hours. (like i siad it depends on how far and complex you want it) So 20 frames is = to 1 sec. so if you want your days to noraml you can apply real logic. but if you want shorted days (i sugest it) then you may have to do some math. By the way i'd like to add you should use the search you can find tuts on things like this all over. but i feel like helping...so...yeah...ok so in the comment event that were going to call day/night, you need to put a wait command. for 20 frames. then under that add a 1 in the Sec. Var.
so now here comes the Conditional branches. make a conditional branch that says when
conitional branch: Var. Sec.s == 60
Var.: Min.s += 1
Var.: Sec.s == 0
Else
now we need a conditional branch for Hours
conitional branch: Var.: Min.s == 60
Var.: Hours += 1
Var. Min.s == 0
Else
Hours conitional Branch.
conitional branch: Var.: hours == 12
Change Tint: 183, 183, 183, 0
Hours
Else
Only a few more...
conitional branch: Var.: Hours == 24
Change Tint: 255, 255, 255, 255
Var.: Hours == 0
Else
i don't have RMXP with me so i don't know if the tint will look good or not.
also, i might of missed something, if i did, tell me. i'm pretty sure i'm ok...but you never know. Good Luck man!