Create a custom date or time format
Select the cell or range of cells that you want to format. How to select a cell or a range On the Home tab, click the Dialog Box Launcher next to Number . Tip You can also press CTRL+1 to open the Format Cells dialog box. In the Category box, click Date or Time , and then choose the number format that is closest in style to the one you want to create. (When creating custom number formats, it's easier to start from an existing format than it is to start from scratch.) In the Category box, click Custom . In the Type box, you should see the format code matching the date or time format you selected in the step 3. The built-in date or time format can't be changed or deleted, so don't worry about overwriting it. In the Type box, make the necessary changes to the format. You can use any of the codes in the following tables: Days, months, and years To display Use this code ...