Legal Question in Employment Law in California

Absolutely not. The hours you worked are the hours you worked, and your boss must pay you for every hour (and every minute).

Document every time your boss does this, including the change that was made. You should speak to an employment attorney ASAP regarding your situation.

Good luck to you.

I agree with the previous answer EXCEPT if what you entered contained errors and the changes made to time card correct. Just because you filled it out and signed it doesn't cast it in stone. If there were any mistakes in your timekeeping your employer has the right to correct them.