How reminder popup is triggered?

[Ashif Malayil]

I have a custom event module. When I create a record, I update the "Date Start" and "Date End" fields and set a reminder popup on time. However, after saving, the "Reminder Popup" field is set to "None," and I am not receiving any popup notifications. What exactly is triggering a popup?

[yuri]

What "Date Start" value do you set? If it's in the past, a reminder won't be created.