I am assuming you are referring to the ExcelXp tagset not XML in general. ODS markup is not specific to Excelxp's SpreadsheetML.
If that is what you are referring to, I would be interested to know which version of the tagset you were using and what sort of problems you had.
I should also mention that the ExcelXp tagset does not work with SAS 8.2.
It was introduced with SAS 9.0. The current version of the tagset prefers
SAS 9.1.3. It can be made to work with previous versions but with limited
versatility.
The column width calculations are not perfect but do work fairly well in most cases. Proportional fonts do not make this an easy task.
For the cases where the generic measuring does not work, there are numerous ways to make the calculation better or to over ride those
calculations and make the width whatever you want. I would be interested
to know the specifics of the problems that you were having.
Also, you do realize that any data, including dates, can be given an excel format. So you are not limited to just dates as strings. Even if no format is supplied, I have not seen any instance where spreadsheeML with dates has not loaded.