Not sure if anyone has encountered this before, but on my Sandbox, the “Date Modified” on my workflows is wrong.

Are all of the Workflows (or most of them) showing a similar date modified? A bit ago a couple people reported a similar issue in here and it ended up being the date of the NetSuite account's last system maintenance (and for some reason system maintenance caused the dates to change on all of the Workflows)

Yes, that was what I was thinking