Car clock random time loss then fixes itself on next restart
 

I have a 2016 buick encore. Occasionally when it was started after setting all night, my clock would be about 15 minutes slow. If i corrected the time it would be 15 minutes fast on next start up. I then realized if i did not change it it would correct itself on next restart. My battery ended up dieing so i went to advanced auto. They said my alternator was probably overcharging the battery when they ran the scanner to test my battery they noticed it had boiled over. i replaced my battey, several days after that i had another auto parts store check to see if my alternator was overcharging. They said it was fine. I am still having the problems with my clock. Any ideas on what may be wrong.

Whatever caused the battery to be boiled out needs to be corrected first.
It could be from overcharging, but the cause needs to be found and corrected first. Bad connections can cause this.
Suggest you have a good shop check your vehicle out and not to rely on Chain Discount stores.