Issues with the Calendar App updating/saving
I thought I should post my findings, in case anyone has the same problems down the line.
I tried a new ROM for my SGS4G: T959V. Everything seemed to be working pretty well, there were a few things I didn't like about it.
Eventually I noticed that I couldn't add to the calendar. As soon as I clicked Save it would be gone and not save to my gmail account. This was even the case when I added to "My Calendar" instead of my gmail calendar.
Everything was checked as far as Settings/Accounts/Sync Calendar but I eventually noticed that even things that I added from a computer weren't properly updating.
Even after re-ROMing the problem wasn't fixed. I tried basically every ROM before I figured out the solution:
There are two apps in the Manage Applications section: Calendar and Calendar Storage. I cleared the data of both of them, waited a minute or two. Voila, the calendar app works perfectly.
I couldn't find anything regarding this problem, so hopefully someone might find this useful if they have my problem.
Be careful if you use the local calendar and not the gmail calendar. Also, why do you use the local calendar and not the gmail calendar?