The Easter Rising lasted from Easter Monday 24 April 1916 to Easter Saturday 29 April 1916. Annual commemorations, rather than taking place on 24-29 April, are typically based on the date of Easter, which is a moveable feast. For example, the annual military parade is on Easter Sunday; the date of coming into force of  the Republic of Ireland Act 1948 was symbolically chosen as Easter Monday  1949. The official programme of centenary events in 2016 climaxed from 25 March  to 2 April  with other events earlier and later in the year taking place on the calendrical anniversaries.. How many years spanned these events?