Why do we try to fool people on 1st April?

Well there are many explanations but I could understand only this one.

Untill 1500 New Year was celebrated on 25th March each year as per Julian's Calender.

Then with the introduction of Gregorian Calender in 1500 AD which we follow to date, New Year was announced to be 1st January . 

But like we all err, there were few ignorant who continued to celebrate it on 25th March!  The fools!

And to make fun of these fools, a common date , 1st April was celebrated from then on. 

May be it should be a great way to open up our minds to correct at least one wrong belief each year and be wiser each year!