Ha! My birthday actually falls on what's estimated to be the most accurate birth date of Jesus. Most orthodox celebrate Christmas based on the Julian calender 13 days after what we consider December 25th on the Gregorian calender. Also note that the Gregorian calender only came into effect in 1582. Looking back at the history that has been recorded, it's quite likely that the actual birth date of Jesus still doesn't fall on what we consider January 7th since the Julian calender's leap years occured on a 3 year cycle instead of a 4 year cycle which means 1 day would be unaccounted for every 128 years. Leap years were counted as follows: 45 BC, 42 BC, 39 BC, 36 BC, 33 BC, 30 BC, 27 BC, 24 BC, 21 BC, 18 BC, 15 BC, 12 BC, 9 BC, 8 AD, 12 AD, and every 4th year from then on. Kepler, Matzat, Radke all argued that the time sequence was incorrect and each came up with their own pattern theories which is why it's so difficult to know for sure where the calenders should've been aligned. Consequently it's extremely difficult to accurantely track down historical events with their exact chronology...
You dont understand the simple math behind the calender you conform to daily and base your schedule and most of your life's decisions on?
Maybe this'll help simplify it for you:
[ en.wikipedia.org ]
check that out and you might actually learn something.