When you type something like 2/2 in a cell, Excel Online thinks you’re typing a date and shows it as 2-Feb. But you can change the date to be shorter or longer.
To see a short date like 2/2/2013, select the cell, and then click Home > Number Format > Short Date. For a longer date like Saturday, February 02, 2013, pick Long Date instead.
If you have Excel desktop application, you can customize the dates in other ways.
If a cell displays ##### after you apply date formatting to it, the cell probably isn’t wide enough to show the whole number. Try dragging the column that contains the cells with #####. This will resize the column to fit the number.
To enter a date that will update to the current date each time you reopen a worksheet or recalculate a formula, type =TODAY() in an empty cell, and then press Enter.