Hi, I'm Nathan.Sorry to hear that you're having trouble, but I'll do my best to help you. Please give me a few moments to review your details here.
The handsets, if all part of the same system (registered to the same base station) will sync up with each other, but it may take awhile for that too happen.
Typically within 24 hours. When a handset is in use, it communicates with the base and syncs that information, so you can try rotating which handsets you use to encourage that process.
For the time, it is only able to use 12hr format for English.