To display the user’s local time, you need to have the user’s timezone offset, so that you can add it to your database’s UTC value.
Some put the day number first, some put the month number first and some put the year first.
The way to do this is to optimize your code so that it detects and displays the user’s local timezone instead of the server’s.
Most english-speaking countries use the 12-hour clock as the dominant written and spoken system of time.
Other countries use the 12-hour clock in spoken time and 24-hour clock in written notation.
But if you have many users who prefer the 24-hour clock, you could display the 24-hour time in a link or icon tooltip that opens on mouse hover.
Time formats aren’t the only issue users face when reading an absolute timestamp.