It's kind of hard to nail down a date to celebrate. I don't remember some of the dates exactly, but you could argue that the day in early-mid June when they decided to do this thing would be the one. They appointed John Adams, Ben Franklin, Thomas Jefferson, and two others whose names escape me to write the document which they did over the next several weeks. That document was presented on July 2 and approved with provision for a few minor changes and those changes were approved on July 4th, so either of those dates would be valid. The delegates left Philadelphia over the next few days and the public was informed on July 8th - that's when the Liberty bell was rung, etc. so that could be a good date to choose too. At that point, not all delegates had actually signed the declaration, and they did so over nearly two months. Choosing the day when the final signature went on could also be a valid choice to celebrate!
In the end, it's a little complicated, but you still have to choose a date ... so the 4th it is!! John Adams was never happy with that, he insisted on the 2nd - and who knows - maybe the 4th was chosen just to tick him off! He was by all accounts blunt, opinionated, pushy and just plain not well liked - today we'd call him a prick! LOL
- Bill