Thanks, Mark. It was nice to chat.
To expand on Mark's update, it was from
Sheets > File > Spreadsheet settings
that we were able to change the file's “locale“, which affected the date format (dd/mm/yyyy versus mm/dd/yyyy).
Another solution may be to be sure you import the CSV directly into Sheets instead of first opening the CSV in Excel and copying cells there to paste into Sheets. I suspect this would work because the Shopify exports use ISO format for the date, which should signify to Sheets that those cells are of date datatype and not simply string data.