so i have made a huge 1024km2 map, and im planning on having a dynamc day and night ive looked at many options but im trying to find a method of using a timeline instead of using a blueprint or what other methods of having an advanced day and night system that i could have weather effects and having fog and everything else working within? blueprint just doesnt seem to be cutting it for setting a time to work with as i always end up just rotating the sun manually
dude, just purchase ultra dynamic sky from the marketplace, that has almost everything you need.
I think Truesky would be perfect for you: https://forums.unrealengine/showthread.php?33944-RELEASED-trueSKY-Alpha-for-UE4-Complete-Sky-and-Weather-System
Otherwise you could create everything by yourself with C++ or blueprints – just combine some few tutorials on youtube + create a own system with a “day of time” value (otherwise you will have to buy such a system) 
What do you mean? You can blend the sky cubemaps if you want.
What you are looking for doesn’t happen out of box, believe me, i have been down that road for over a year, and just hopped off because there is no solution.
Here are your options:
TrueSky: The completely broken sky system that runs on luck
Truesky has no weather system that works. Well, unless you want rain 100% of the time, or not rain 100% of the time. The day/night works, but, the rest of it has been broken for about 3 or 4 years now. Take a look at their support thread. Not good. You will also take at least 20FPS out of performance, nothing you can do there. Unless you are using flying or some sort of “need” for volumetric clouds run by a massive performance dice roll, it isn’t something you need. (see c++ vs. blueprint tests). Also you “can’t” use postprocess with truesky. Maybe its “you shouldn’t”. That came from the developer (see support thread). It’s also $150 for a plugin where you will only use 10% of what it claims it can do.
Ultra Dynamic wont work either, has only day/night cycle, you wanted weather. I think its like $30 or something. Used it for a bit, its nice, just no weather.
Orbit has what you might need, and, works. Its got a lot of work to be done to it, and, is anything but pretty. Personally, the clouds look terrible. Performance is much better then TrueSky, and, hes got a ton of features. Doesnt give the standard “oh, i dont know” or “oh im new so, i have no idea” answer like the TrueSky devs will give you.
Super Genius Weather Effects is pretty, but, its only weather and, as far as i know, cant be randomized (but i didnt attempt because i moved to TrueSky. Looking back … i should have stuck with this and got a cheaper d/n cycle setup and combind). I got it a couple years ago and never was able to get it set how i wanted, so, we scrapped it. Also i think support was dropped on it after 4.16? Sad because it was neat, and support was amazing when i did have questions.