Date Reminder Email Script

Hey All,
Thanks in Advance for any recommendations! Here’s my problem
My company manages medical certifications for about 300 employees, it is important that our staff is reminded when it’s time to renew their certifications. I’m looking for a simple online script that I can put a date in, and it will send a reminder email 90, 60, and 30 days out.
Does anybody have any recommendations?

Well, there are multiple options out there. Simplest is perhaps google calendars where you can invite to the employee whose certificate is due to expire on that date.

Alternately you can also use google sheets with google scripts where you can do a check and send an email

If you want to go a step further, you could write your own script.