When the user's spreadsheet has detected fields as dates, it might formate them into numbers interpretable as several date formats.
So, in the file, these values are not really the ones we read.
In Fusion, the value might be written this way : yyyy-mm-ddThh:mmZ.
As a consequence, to avoid this, we have to lead the spreadsheet to rewrite it as a purely textual value.
For the moment, one methode has been identified for this purpose in 2 spreasheets. One with LibreOffice, one with Excel. The methods are distinct from one spreadsheet to another.
LibreOffice (3 steps)
1°) Select and cut all the dates:
2°) Then paste them at the same position as an Paste Special > Unformatted text:
3°) Then, deactivate "Detect special numbers":
Microsoft Excel (6 steps)
For the moment, unfortunately no simpler technique has been identified.
1°) Select & cut the date column:
2°) Create a new sheet in which paste the dates :
3°) Then, in a nearby cell, apply the formula: =TEXT(B4;"dd/mm/yyyy")* to turn the number, formatted as a date, into a text.
* Replace B4 by the first date cell
4°) Extend the formula until the end of the list:
5°) Copy the column then paste it onto the original sheet, at the dates' location:
6°) Delete the sheet created at the begining of the process.