1-2015 When did it all start ?

On Christmas Day (25 Dec.) I posed myself the question >> "When was Jesus born ?" . More out of curiosity and perplexion as a maths teacher. The question was repeated and published on the Internet, for all the world to answer ::

http://partha-the-prof.blogspot.in/2012/01/32012-when-was-jesus-christ-born.html

http://partha-the-prof.blogspot.in/2012/01/82012-when-was-jc-born-sequel.html

Now, almost three years later, I get a clue from someone who knows more than me on these matters :: http://aristean.org/birthmay23.htm

Then, why did someone start the confusion with 25 Dec. ?

There is also confusion on the :

date of crucifixion of JC

The whole question is much more fundamental, and of serious tenor when we ask "When exactly did CE start ?" Are we following a calendar which is of questionable origin ?

I am still confused.

partha