More advice on turning off alarms (or, colloquially, notifications)
iCal preferences. Check the 'Turn off alarms when iCal is not open' box, and as long as you have iCal closed you won't get any alarms.
View attachment 45170
Thanks to blodwyn for the suggestion to try Preferences > Advanced > Turn off alarms when iCal is not open.
Now (years after his/her post) apple seems to have added a new option, i.e. Preferences > Advanced > Turn off *all* alarms. (Which was not present in the screen shot that blodwyn provided).
So, try that. It might help.
In spite of that suggestion there are some caveats:
I created a test calendar entry with like 7 alarms each 1 minute apart and then selected "Turn off all alarms." The alarms kept popping up! Argh. Then I thought maybe this is because I created the event *before* selecting "Turn off all alarms." So, I made sure "Turn off all alarms" was truly set and *then* created another event with like 7 alarms. These alarms did not go off. This suggests my hypothesis is correct.
However, if my hypothesis is correct I am still suffering from this iCal misfeature. This is because I have a presentation on Friday. I have *years* worth of reminders that go off at random times already on my computer. These will (according to my hypothesis) continue to go off even now that I have selected "Turn off all alarms" because, of course, they were created long before I made that selection.
So, wish me well when I give my presentation when the audience sees lots of random reminders! (Or else I will have to painstakingly delete them beforehand).
Alternatively, perhaps my hypothesis is incorrect and I have actually succeeded in turning off my alarms once and for all. (But then why did I get the above behavior with my two test calendar entries?)
As the hours / days pass by I will no for sure whether I have truly silenced my alarms so I do not have to embarrassed by random personal reminders popping up while people are seeing my screen.
One more pointer (which might help google searchers like me find this advice?):
I was wanting to turn off the alarms on my system. I got confused because at first I thought they were notifications and so I would go to View > Hide Notifications and would frustratingly still get the stupid things popping up...for months / years!! Now, on this the n-th attempt I realized it was probably not notifications I needed to disable but alarms.