I have a Pixel XL running the latest version of Android. The alarm icon is persistently showing on the right hand side of the status bar, but I have no alarms at all. When I pull down the notification drawer, below the time and date shows an alarm set for up to 10 minutes from the current time. If I touch this, nothing happens except that the alarm time resets to exactly 10 minutes from the current time. I.e., if it is 12:07 and the alarm shows for 12:10, when I click on the alarm in the notification bar it will then show 12:17. If I don't do this, the alarm doesn't actually go off. If I do nothing, at 12:10 the alarm will just automatically reset to 12:20. This carries through the OS. For example, in Do Not Disturb settings, it will have the option of 'Until next alarm' and use this non-existent alarm as the end time.
I've cleared the cache to the entire device, cleared the cache to the clock, removed all apps that have any sort of reminder/alarm functionality besides the stock Google apps like Calendar, Keep, Now, etc.