Why is my Android Calendar forcing reminders even though I've disabled them?

[AC Question]

I have a weird problem. Whenever I create a new event on my Android calendar in my phone (Samsung Galaxy A3 2016), I make sure it doesn't have a reminder on. Still, after some time if I check the event in question, it has automatically added a reminder for it. Sometimes it doesn't happen but most often it does and if I fail to notice it on time, the reminder appears on my phone screen. And that's not all, the reminder is ALWAYS set on 23:30. (From this I've deducted that perhaps this problem is only with the events I've set on to concern the whole day.) I've checked a million times from the settings that I have disabled all the reminders and as I said, I have made sure that the events in question do not have the reminder on when I create them. What is going on, can anyone help?? This is super annoying since I often wake up to the reminders.