If you type the number 1 in an Excel worksheet cell, then point to the Short Date format on the Excel Ribbon, you can see that date in the formatting preview.Since Mac Excel 2011 it is in line with the Windows date.Up to and including Excel 2008, the date system started on January 1, 1904.

The date system in Microsoft Excel for Windows starts on January 1, 1900.There are date system differences in some versions of Excel. If you format negative numbers as dates, the cells will be filled with number signs. Note: Only positive numbers can be formatted as valid dates. The imported dates are probably stored as a text value, instead of real numbers, and that is causing the formatting problem. In Excel, dates are stored as sequential serial numbers. Why won’t the imported dates change format? Why won't they show a short date, without time included, in the cell's formatting? Those dates stay in the same date/time format, no matter how you try to format cells that contain those dates. However, the date format for the imported dates in column C does not change.Using the Number format commands on the Excel Ribbon Home tab, the Short Date format has been applied, from the number format menu.The time shows hour, minute and second = hh:mm:ss with AM or PM. The date is in short date format - d/m/yyyy. In the screen shot below, Column C contains imported dates, which show the date and time, separated by a space character.

Definition dialog box launcher