Spreadsheet column update with the wrong value - Google Spreadsheet integration issue

Hi, 

One of my clients use your service on its website and he encounters an error on the submission date in Google sheet.
As you can see before march everything was fine and then the error appeared. 
At first I thought that the issue was the date format an that it was a timestamp but it appears to be something else, any ideas ? 

Hello,

I think this might be due to a modification from the spreadsheet. You can try to remove the integration and add it back again. Usually that should be enough to fix the problem.

If the column still populate with those numbers instead of the date format after re-adding the integration, please let us know.