Restore to earlier time I recently got an Android update and don't like it AT ALL. I have a Samsung Galaxy S4. Is there a way I can uninstall the update?
Restore [Android] to earlier time?

As far as I know, you can restore to an earlier time (in case of Android update) only when you have a Nandroid backup, and it seems you don't have it so the answer would be no for you sadly.

Is there a way I can uninstall the update?

I don't think you can ever uninstall a system update (not that I ever heard yet) because it seems Android unlike Windows OS doesn't create a restore point, so you can't track where the updated files went into system, which overwrote the others and so on.
You can try a manual way by extracting the update and analyzing which files this update will overwrite or did so, then download previous Android version you had, match the files and copy them back into your phone, reset and see what happens. As it is obvious, you need root access or a  custom Recovery and there can be data loss or a soft-brick.
I also saw some threads on a forum (in case of OPO only) where folks used a previous OTA update to revert back to earlier system. E.g. If the system update pushed you from 4.3 to 4.4, or 4.4.2 to 4.4.4, or any minor update, then previous OTA (flashed via Recovery) kinda worked for them. Note that this is dangerous and I don't recommend it. A major update like 4.4 to 5.0 and reverting back to 4.4 via forced OTA could result in hard-brick.
What can you do?
You can ask your OEM (technical support) to flash the older Android release on your phone, or, you may get your hands dirty and do it yourself. (The latter may void warranty, check your OEM's policies towards flashing.) If you choose the latter than take a look at how do I search on this website, or head over to XDA, type your device name and see results.
It could be possible you can flash your system without voiding the warranty, if you download a ROM of previous Android release signed by OEM and flash it via Stock Recovery. Try it (take backup always).