Actually, come to think of it, you can use Google Calendar to schedule Make scenarios!
Did you know you can create email notifications in Google Calendars?
Now all you need to do is to create a “Custom Mailhook” to filter out only those event email reminders to run the rest of your scenario!
1.
Here, I have created a test event with an email reminder 15 minutes before
2.
I received the email in my Gmail account, exactly 15 minutes before the scheduled event
3.
Set up a Custom Mailhook as scenario trigger
4.
Use a filter after the mailhook to filter event email notifications only
For more information about setting up a custom mailhook, see https://www.make.com/en/help/tools/webhooks#custom-mailhook