GUI method , does not always work
Go to Settings > Language and Region. You will see something like
Then click the unblock button and enter your password. In formats select your correct region and language .It is India (English) for you , I set United States because there isn't a English format for my location and I think that this is a bug with elementary OS.
Click the Set System Language button and then the Set Language button
Logout and back in to see the changes. Restart to see the changes on the greeter
Terminal method , always works
Run the following in a terminal
For your location it is
localectl set-locale "LANG=en_IN.utf8"
For my location it is
localectl set-locale "LANG=en_LK.utf8"
For other locations modify the command