Why would you laugh at 0000-12-25? Is it because of the mix-up of dates and year lengths between different calendars or something else?
Even as an atheist, I have to believe that for such a story to hold for over 2000 years, there has to be someone named "Jesus" who was born about 2000 years ago, messiah or not.
Its not the idea that there was some guy named Jesus born around then who was probably some type of preacher/prophet/messiah/cult of personality/whatever that I was laughing at of course. It was the fact that even as 10 year old I knew that the date December 25th was arbitrarily set by some church at some point and setting that date in order to "go see" Jesus' birth is quite a clever joke. Discussing this with my fundamentalist friend and finding out that he believed that Dec 25th was the actual date of the birth was quite the revelation to me (no pun intended). After that we discussed many more tenets of his fundamentalist beliefs and I was shocked. I had no idea up until that time that anyone could teach their kids such pointless crap and the amount of mental gymnastics required to hold on to those beliefs. It was a very eye-opening experience for me.