From "The Tale of Years":
T.A. 3018 (S.R. 1418)
April 12: Gandalf reaches Hobbiton (in "The Shadow of the Past");
T.A. 3019 (S.R. 1419)
April 6: Meeting of Celeborn and Thranduil.
April 8: The Ring-bearers are honoured on the Field of Cormallen.
T.A. 3020 (S.R. 1420, the "Great Year of Plenty")
April 6: The mallorn flowers in the Party Field.
Thanks! Not a lot happens in April, though...