What is time format set to on GC - see https://connect.garmin.com/modern/settings ?
Seriously Garmin has had this problem for over three years and can't figure it out? My Fitbit doesn't have this problem. It is incredibly annoying! I am a nurse and we use military time at work. My previous career was airline, also military time. I try to use this for my watch at work but this problem makes it impossible. I can't believe Garmin allows a problem to continue that effectively alienates anyone who works with military time.
My Garmin syncs to my Phone and I noticed that Time format and Move bar started changing this has only just started happening – I have changed the settings in the software on the phone then synched to my watch and the problem has gone away.