মাস/দিন/বছর এর পরিবর্তে দিন/মাস/বছর করে নিন

First, let me recollect how we changed date formats in Windows XP and Windows Vista.
For all Operating Systems,
you have to go to Regional and Language Options in Control panel.

But in Windows 7 you may get confused with first Regional and Language Options screen, which is shown below.

This first screen is very similar to Windows Vista ‘Customize Regional Options’ which you get after press ‘Customize this Format’  in Vista. See the below Screen.

Ok, don’t confuse too much. What I’m trying to say is, when you see the first screen in Windows 7 Regional and Language options screen you may try to edit short date format to dd-mm-yyyy ( I did already) how did in Vista. But you can’t change like that in Windows 7. By clicking drop down arrow mark next to short date will allow you to select any of the pre entered entries only. You can’t enter your desired date format here.
To do it, click on Additional settings button, then go to Date tab and enter your new date format in Windows 7.

To make it short; to change date format to dd-mm-yyyy in Windows 7,

1)      Go to Control Panel
2)      Regional and Language Settings
3)      Click on Additional Settings
4)      Go to Date tab
5)      Enter new Short Date Format.

কম্পিউটারের তারিখ লেখা এবং দেখার ডিফল্ট ফরমেট পরিবর্তন করার উপায়, How to change the default faormat of system date