Day and Night System, I'm looking for the perfect system Options

[MEands]

Simply put, I'm trying to think up a system that allows you to enter the same areas at daytime, and also at night.
I don't mean having a clock system, but like...there's always such a different feel to towns and fields when it's at night.
I want some form of changing time, but the player should experience it, not an event driven "it's night now" sequence.

Night just brings out so much atmosphere, I'd really like to hear your ideas of the perfect system.

(My brain is tired today, tell me if this is confusing)

[MEands]

At certain points in the game it is required that the events take place at night.

I might just do it the cheap way by using events, if you find a bed you can sleep and wake up at night.