I’m assuming this solution won’t work since you want to know if the door was opened, even if it’s already been closed.
The SmartApp below isn’t meant for this purpose, but I’m pretty sure it can do what you’re trying to.
If you set the last event notification threshold to something like 10 minutes it will immediately send a notification when you save the settings, but it won’t send another notification until 10+ minutes after the next time the door is opened.
You can’t set a specific time to send the notifications, but you can limit the notifications to a specific mode, like Night mode, which will delay sending the notification until it’s in that mode.