When Excel formats dates, times, and numeric values, it looks to the Windows regional format settings. When you change these settings in Windows, it will automatically carry over into Excel.
Open the Control Panel.
Click Change date, time, or number formats.
The Region dialog box displays. Any changes made here will automatically be reflected in Excel and other applications on your computer.
Select the regional format you want to apply.
Notice you can preview examples of the formats based on the settings you picked at the bottom of the window.
Click the OK.
Dates, times, and numeric values will automatically reflect these changes in Excel the next time you open the program.