Yes—do this on the files locally before uploading. Google Photos does not provide a way to bulk rewrite capture-date metadata for images already stored there.

A common tool for this is ExifTool. Based on the answers provided, you can write the filename date into the standard photo date fields with a command like:

exiftool '-Alldates<Filename' .

This copies a parsable date from the filename into the image’s date metadata fields. It works best when filenames consistently contain dates such as YYYY-MM-DD or YYYYMMDD.

If you prefer a graphical tool, one community answer mentions a simple app called “Creation Date Changer.”

Best practice: test on a small folder first and keep backups, since metadata changes are usually written directly to the files.