If it's a date:
* July 14, 1798 (Use a comma to separate the day and year)
If it's part of a sentence:
* On July 14, 1798, the French Revolution was at its peak. (Use a comma to separate the date from the rest of the sentence)
* The Battle of the Nile took place on July 14, 1798. (Use a comma to separate the date from the rest of the sentence)
If it's a heading or title:
* July 14, 1798 (Use a comma to separate the day and year)
It's important to note that using a hyphen is incorrect in this case.