An alarm is something that warns or signals, by one definition. It doesn't necessarily need to be urgent.

However, Google is weird. At least on my phone, I can easily set a timer for 3 days and 5 hours without a problem.

Alarms on Google typically mean wakeup alarms. That may trigger the snooze/cancel functionality when that timer expires. Odd that you can't set one way ahead of time.

I am not trying to be a jackass here or anything, but I have never actually thought about the distinctions between alarms, timers and reminders. I just kinda thought they were all the same. /shrug