The format you enter may differ on region and language of your Windows and Excel installations.
To change to the format you need, please follow the steps outlined below.
1. Select any cell or cells you need to modify date format.
2. Press Ctrl+1 to open the format cells dialog box.
3. Choose date options as shown below. I have chosen English (United Kingdom) as Locale (location) in the screenshot. You can choose the locale of your choice. And then, you can choose the specific format whether it is DD/MM/YYYY or DD/MM/YY.