In the default calendar app press the big + icon in the bottom right. Next press the text to the right of the bell icon. Under alert time select none.
Hit where it says ten minutes, then you can turn it off. If that doesn't work, go to settings and go to notifications, hit calendar, then turn of notifications.
I guess I should be more clear with it... I want it to default to no alarm, but didn't find the option. I honestly gave up on it and just went back to Google calendar anyways... I miss my pixel