This tutorial shows how to change date format in Drupal 7.x.
To manage date formats in Drupal, you need to manage both format types and formats themselves in the Regional and Language settings.
Navigate to Admin > Configuration > Regional and Language > Date and Time and click on the Formats tab:
You can create a new date/time format by clicking on the Add format button on the top left using the standard PHP date/time formatting tokens:
Once you’ve created your new format, you can assign that to a format type by clicking on the Types tab (admin/config/regional/date-time) or you can use format from the list:
Feel free to check the detailed video tutorial below: