Strange date formatting issue in 365 version

[IslaBee]

Hi,

I have a spreadsheet with a number of power queries which loads data into various tables. Spreadsheet was created in Excel 2016, and works fine in that version. However, if I now try and update the queries on my Office 365 version the new dates entered do not format correctly in the updated tables, they now show up as code and I need to reformat each table (which is a pain as there are over 30 of them).

Is there any reason Office 365 is doing this, and any way to fix it?

Thanks

Isla