this, I don't have lol so not sure but the route I have heard working

make sure 24-hour time is ON

make sure in the app the calender is set to Gergorian

but

I know your trying to get away from 24hr time, so since this was a known issue it might have been fixed in an update? have you checked that your on the most recent firmware for the band?

you could also unpair the band and then restart your phone and pair it but I would check firmware updates first