Alarm goes off at midnight & repeats for half hour,...

I have not used your particular model, but had others that are similar to it.

Many of these watches have more than one alarm! I have one by a different manufacture that has three alarms. I had the same problem.

Unless you get the other alarms in your watch to show, you will not know if they are set, and what they are set to. Midnight is the default setting on many of these alarms. It is the 00:00 hour of the day. When most of these watches are new out of the box, they will have their alarms set at midnight. (This can be annoying for the average person).

Refer to your instruction manual about multiple alarms. Most of the watch manufactures also have downloadable instructions on PDF, and also have demo sites about how to set their watches.

Jerry G.