Max2 I agree with Automatic Apple. Need more info. Which iPad, what is the other app, what device are you wanting to sync with? How tall is the Empire State Building, true or false?
I use Calendars 5 on my iPad (IPad Pro 12.9 2nd gen and iPhone 7 Plus) but i used Google calendar for a little bit and it synced between my two devices much like push mail. Make a change on one device and within a few minutes the change was on the other. It’s been awhile but I believe the sync setting is in Google app. I don’t have a desktop or laptop but i would imagine syncing with one of them is just as easy. Hope this helps.