Well. It's getting dark outside, and the bad wolves and monsters are coming to attack the innocent player... What we had at day, the lovely butterflies, the giant bugs, and the number 7 are nothing compared!

This sounds like a nightmare for an adventurer than building an arcade/action/misc game as a programmer, but I'll explain this you, so maybe I could bring you to figure out how to make a day into night and a night into day!

First... There's 2 ways:

NastyMan's way:
NastyMan... (Me actually) wanted a credit for his system, so here I mention myself...
Take a clock object and a counter... Set the clock defination to 24 hours... Then set the counter to retrive the clock's hours...

Make sure that you have day time active objects textures & backgrounds as same as night time ones...

Set an event: If counter value is > 18 (Which is the hour that I set for my time zone at winter...)
Another one in the same line: If counter value is =< 24
(Just for bug safety)
A last one: If counter value is < 6
- then paste night time sprites into background as obstcles/not an obscle(As you define what sprite is what...) + destroy/hide(Make invisible) all day time & night time sprites
+Destroy all butterflies, Fluffy monsters, furry animals, and young attractive little girls... or if you prefer to create objects instead of placing them, then: Create fox/wolf, in X,Y... create a Children's deviant in X,Y(Yeah... You choose the spot... X for horizontal, Y for vertical... You know!) rabied canine at another X,Y
And a drunk alcoholyst who shoot darts on you in yet another X,Y spot of screen...

That set's for tonight...

For today:

Set an event: If counter value is >= 6
Then Set an event: If counter value is =< 18
Set this:
Paste Day textures and sprites into background as obstble/not an obstcle.
Destroy/hide(Make invisible) all textures and sprites...
Destroy: aliens, predators, wolves, deviants, pedophiles, drunks...
or... If you prefer to create than destroy... (Why we should destroy anyway when we can create? make luv!... & Sex!)
Create: Baby pissing in a cradle at X,Y
An arousing semi naked little girl at X,Y
A Butterfly at X,Y... A Bunny at X,Y And a sex stall(Open from 6:00 to 19:00) at X,Y...

(Yeah! I like the day more than the night cause it's sexier and I don't like to be attacked at night by these nasty guys outside!!!)

The second way (Should also was found by NastyMan... Great skies!) goes this:
Make same object for day time and night time... The day time is in direction 0... The Night time is in direction 1...
Set an event: If counter value is > 18
Another one in the same line: If counter value is =< 24
(Again... Just for bug safety)
A last one in a different event: If counter value is < 6
Change the direction of your sprites into: 1


Set an event: If counter value is >= 18
Set an event: If counter value is > 6
And change the direction of your sprites into: 0
(Why touching them actually?)

Settled!

Anyway...
what if your'e using a moving backgrounds?
I use Active System Boxes as moving backgrounds! And be sure it works on active pictures too!

How to set an Active System Box as a pattern background?
You'll see an Image option in the Active System Box's defination screen: Change it to pattern... Then set the border color into none... And I hope you'll not get that issue called border-line again! Cause it can be disturbing in the game... Though Day-Night relations sounds erratical too!

Get here a small bonus tip:
When player press <- on joypad: set position of Active Sysyem Box to Active Sysyem Box -1... When joypad is pressed -> do the same, but now add a +1... You can change the numbers until you got the prefered result! I recommand to copy & paste the last 2 events again, so you'll get a smoother effect! MMF does runs it faster though set position of Active Sysyem Box to Active Sysyem Box +1/-1 event is placed twice now! (A dirty side effect from MMF I guess) =]

For changing day time or night time with the moving active system boxes you've set, just make the Active System Box of day invisible at the night time, and the Active System Box of Night Invisible at the day time...

What so funny is that you can make it with music too!
First set the hour defination compared to what you've got in counter.

Then:

On night time you can play a night tune midi
(Or a Module!)
On (The so sexy!!!)day time you can play a day tune midi
(Yeah! Or a Module! And it can be sexy, with vocal woman voice sings and/or moans!)

I usually sets a counter instead of just asking the clock what hour it is to make it bug safe, though I assume that it works directly with clock object too... Anyway, I recommand to set the counter Max value to 24 and the Min Value to 0... or don't even touch it! Well... You choose! Think wisely! You might end with a day time enviroment when it just swiched into night-time just because you didn't touched it, or destroyed textures instead of making them invisible! =]

That's what I seems to know & remember!
Now try that! Enjoy!

Tough my humor was abit Nasty here... I can't afford myself acting like a praist who never wanted to sin... It will be a crude lie... I admit that I sometimes still wish that I had a young maid with me for the night time... Uha, I mean... The day time... =]