Crossword Clue:

the act of celebrating

AnswerCrossword Clue
LEX"The Joy of ..." (book celebrating wordplay)
TETHoliday celebrating the arrival of spring
SIGNALCORPSBranch of the Army celebrating its 90th anniversary.
JULMo. of the Hopi Niman Kachina Festival celebrating the harvest
SEDERFeast celebrating the Exodus
SCOTOne celebrating the holiday Hogmanay
SUKKOTJewish holiday celebrating the fall harvest
IOOTHANNIVERSARYThe ice cream cone is celebrating this
SEDERRitual celebrating the Jews' liberation from Egyptian slavery
JETSETTINGCelebrating the New Year in different time zones, for example
ALASKAState celebrating its 50th anniversary in January 2009 (and a hint to the three theme entries)