Simplify the following text for a Grade 8 native English-speaking person.
Original: Constitution Day was first held on 9 July 2000 to mark the centenary of the Constitution in the lead up to the Centenary of Federation , although commemorations were low key and were not widely held after 2001 .
Simplified: Constitution Day was first held on 9 July 2000 to mark the centenary of the Constitution as part of the Centenary of Federation . The celebrations were not big and have not been widely held after 2001 .