Specify exact date/time for reminder

[nofishonfriday]

Checklist

• [X] I made sure that there are no existing issues - open or closed - to which I could contribute my information.
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• [X] This issue contains only one feature request.
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Feature description

Currently it's only possible to specify minutes/hours/days (when entering a custom value) before event start for reminders. While this works it would be more handy if I could specify an exact date and time for a notification instead.

Why do you want this feature?

As usually I prefer to have a notifaction say one or two days before an event at a specific time I currently have to calculate hours manually for when to set the notification.

Additional information

No response