Android Central

Rather have a 24-hour clock instead of a 12-hour clock? Or have the day appear before the month? Changing time and date options are very easy, and can be done on the fly. By default these options are set to be 12 hours and a MM/DD/YYYY style, and the time is set automatically by your carrier. To take complete control of these settings simply launch your settings, then scroll down to Date & Time settings. Unchecking the automatic will give you the option to manually change the date, timezone and actual time, along with the option to use 24 hour time and selecting the date formatting.