You may encounter a problem with dates changing when you connect to an Excel spreadsheet in Tableau if:
- You are using Excel for Macintosh
- You are using Excel for Windows from 2000 or earlier
The cause of this problem is probably that these earlier versions of Excel are using the 1904 date system, while Tableau uses the 1900 date system.
The simplest way to avoid this problem is to use to a more recent release of Excel. Also be aware that even the more recent releases of Excel offer the option of using the 1904 date system; however, you must select the option on a per-workbook basis. To make sure you are not unintentionally using the 1904 date system for a workbook, you can check in the Excel options:
Step 1
With the workbook open in Excel, click the Office button and select Excel Options.
Step 2
In the Excel Options dialog box, select Advanced.
Step 3
Scroll down in the Advanced options to When calculating this workbook.
Step 4
Clear the Use 1904 date system check box, and then click OK.
For more information about this issue, see these articles in the Microsoft Knowledgebase: