While we are rarely given an exact number of days that happen between most events in One Piece (like when we get “a few days later” between arcs), if we assume most of these unspecified intervals are 5-7 days and we add them to the time we know happens (such as the month between Marineford and the timeskip) then we get around six months between Luffy setting sail and the timeskip.

This means five months between Luffy setting sail and Marineford.

If Luffy set sail on his birthday, May 5th, that means Marineford happened on early October.

Ace and Whitebeard died around Marco’s birthday.