I've stopped modding GTA:IV. The reason why can be found here

Current version: Beta 2

What is it?

You can now lock, unlock, and change the time of day. (NOT the timescale. You can not "freeze" the world.)

Install

Should be used with GTA:IV v.1.0.2.0 and .Net scripthook 0.86.
Put it in the ./scripts folder.

Functions

-Console command: "SetTimeTo". Set time to a specific value. (ex.: SetTimeTo 23 56)
-Console command: "LockTime". Locks the current daytime.
-Console command: "UnlockTime". Unlocks the time.
-Keypress: Lock / Unlock the time (standard "T")

Customizable: (in LockTime.ini)

-Which key to use (if any)
-Lock the weather?
-Go to "real" daytime after unlocking?

Why?

Might come in handy for machinima, or just for fun (I don't like the night time 

Thanks to

HazardX for his .Net hook.