When I download your packaged workbook, the dates are null for me. Apparently the same phenomenon as you see when you upload to the server. So frankly, I'm not sure why the desktop version of your workbook ever worked for you.
Here's the problem: although your date columns are formatted as "Date" in Excel, they're not actually dates — they are string values. And, they are in a format that both Excel and Tableau are unlikely to properly interpret as dates automatically (because of the dot notation used).
For this work, you need to do one of two things:
OPTION 1 — rework your source data so that the dates are true dates in Excel. You can test this by running a formula VALUE(B2) or VALUE(C2) and make sure that the result is an actual number rather than #VALUE!
OPTION 2 — bring the data into Tableau as-is, but mark the date columns as String data type, then build a date version using a calculated field. For example:
thanx for your quick response!
Interesting to see that the packaged workbook is not working for you ... I guess you have your computer localized with the US settings?
You where right the date was saved as a string. For some reason my desktop version seems to handle that issue only the server not
As a fool proof variation of your Option 1 I converted the date into numerics and saved them that way.
When importing the data, Tableau is able to figure out the correct date when variable type is set to date.