The Date/Time title cannot be edited.
However, in Motion, if you add a Time Date generator to your project, turn off Animate and publish the Time Date value, then in Final Cut, you can add the template to the project, then double click on the first value of the Time Date parameter, type in the month, type a period or tab, type the day, period or tab, year, etc. When you get to AM or PM type an 'A' or 'P'.
You can publish the Time Format and Date Format parameters if you like. However, the Time Zone you get with Time Format > long is the time zone you have set in system preferences for your current location. There is no way to change the template without changing your system settings.
If you'd like to save yourself the trouble, I've already done it and it's available here:
https://fcpxtemplates.com/sc-date-time
There's a sampler of some of the different formats that are available.
You are under no obligation, or pressure. I've already given you the basis for making our own above. The rest is just window dressing. If you take a look at SC Date Time, read the section Odd but true, and consider that information for the type of template you build.
