jessie and stretch are installed on same PC
time of jessie is wrong: Fri Oct 12 21:51:05 CST 2018
then i reboot and enter stretch
time of stretch is right: Sat Oct 13 05:55:30 CST 2018
tzdata of both are reconfig to same place
Is it possible that one is set to "Local Time", and the other to "UTC Time"?
I had that problem once, Dual Booting Windows XP (I'm Dating myself) and an old version of Ubuntu. Turned out to be an Education Issue: Everything was fine, when I changed Linux to "Local Time". (Your issue may be the opposite).
I forgot what I did to fix it. (So Long Ago. LOL!)
Good Luck and Best Regards,
Kenneth Parker, Computer Consultant