When setting a date in a cell using SetValue(DateTime), the value should be converted to its numerical representation before adding it to the XML. However, it is currently written as a string. This causes issues when opening the generated file with Google Sheets - the dates are not visible in the file.

A customer also reported that this is causing issues when the file is opened with MS Excel in specific cultures, but we were unable to reproduce that locally.

Workaround: Convert the DateTime value to a number before setting it to the cell:
cell.SetValue(DateTime.Now.Date.ToOADate());