File Date Changes to Backed-Up Date - Normal Behavior?

I’m rewording my problem in hopes that someone will be able to help. I have files on a PC that were created on 7/10/2010 for instance. When I backed these up to a My Book 4TB drive using WD Backup software, the date of the file got changed to 8/17/2017, which was the date I backed up the files.
Is this normal behavior? I’ve used other external back-up drives before, and not had this problem.

Thanks for the help.

Hi DaBrownCO ,

Yes, it is a normal behavior. Since you create the last backup on 8/17/2017 that is why it is showing the last modifying date.