Hi @twinklemagoo. Welcome to the Wappler community 
I’ve never used Bubble so I’m possibly not the best person to respond. However, I’ve read plenty of posts from Bubble and ex-Bubble users so I almost feel like I’ve used it!
What you’ve asked sounds to me like the Wappler equivalent is a CRON task. You create the backend API script (Wappler calls this Server Connect API) and then set up a CRON on your hosting server to run that script every x minutes/hours/days/months/etc. You would put a condition in that script to do the 90-day bit but probably set it to run once a day. Wappler gives you the path to the script so it’s easy to set up.
I believe NodeJS has scheduled tasks built into Wappler so you wouldn’t use a CRON but do it all within Wappler instead. But I’m not 100% certain of that.
EDIT: I was right, read about it here: Scheduling Actions with NodeJS
I hope that helps. You’ll soon be glad you made the move.