One of the most challenging aspects of writing the date is knowing whether you should use a comma. It all depends on the format. In the month-first format used in America, use a comma after the day and before the year: January 4, 2005. In the day-first format used in Europe, you don’t need to use a comma.
However, with either format, you’ll need to use a comma after a date if it is part of an introductory phrase:
Correct: On January 4, 2004, Geeta was born.
Incorrect: On January 4, 2004 Geeta was born.