I am a Malaysian and so my location is Malaysia but I want to change the language of the date-time in the login page to English instead of Malay? Any idea?
This should work but it's more of a workaround than solution and I haven't personally tested it. Try changing your language to English in Settings and then use button "Apply to login screen, guest account and new users". Later on change back to Malay on your account and don't use the option to apply Malay to login screen.
The result should be English as system wide and Malay as local user language, meaning that whole login screen, including date will be in English.