According to Genesis 1:14-19, YHWH created the Sun, moon, and stars on the 4th day of the first week.

Does this mean that the first month started on the 4th day? Or that the moon was not created until the 4th day of the first month?

It says the moon was created as a lesser light to govern the night so does this mean the 1st moon was a full moon? Making the first day of the first month a full moon? Or does this mean the 4th day of the first month was a full moon?