Same prob with my watch, there is a manual on the web, you can find it by searching 7t27 7a20 pilots chronograph - I Printed it off but don't remember the address. You can syncro the 24 hr dial by rapidly advancing the minute hand in a clockwise direction. I noticed if you turn it anti clockwise it screws it up again. Also if the stop watch starts to zero somewhere other than 12 it can be adjusted by pulling the time set out to the second stop, then using the start/stop and zero buttons of the stop watch to rezero the second or minute hands of the stop watch.
Hope that helps
Al