I can only see Default alarm (minutes) set to 0. So i guess i don't have an alarm setup. But i don't need one. I don't need to be reminded about an event prior the event, i just want to be notified when the event happens.
And this works for every other event i have. I just open New event window, clear the All day event checkbox, set a date and time, add Summary, maybe select a different category or just leave it as Default and hit OK. When the time comes it shows the popup on the desktop. I have an event, which is set to show at 11:30 on every first Saturday of the month and today it showed the popup. So option with "First day of the month" is working fine. And on March 30th the one with the "Last Sunday of the month" didn't show the popup. maybe it is related to daylight saving changes. Though it didn't worked with Last Monday of the month on March 31st either while i was testing. Will have to wait till the end of the month to do testing. Or i may try to test this in a virtual machine, if i'll have time for this.
Btw, i'm using a template for new events. Thinking maybe that's the cause, because i think last time events worked fine with "Last day" option and i have made a template maybe a few months ago. My template is only clearing the All day event checkbox and setting category to Default.