* 1741: Handel started composing "Messiah" in Dublin, Ireland.
* August 1741: He finished the first part of the oratorio.
* September 1741: The second part was completed.
* October 1741: Handel worked on the third part.
* April 13, 1742: The first performance of "Messiah" took place in Dublin.
So, technically, the composition process of "Messiah" began in 1741 and continued into 1742.