Answer: leapday

AnswerCrossword Clue
LEAPDAYAdd-on of 2004
LEAPDAYQuadrennial bonus
LEAPDAYSixtieth day of the year, periodically
LEAPDAYFeb. 29
LEAPDAYMarch preceder, periodically
LEAPDAYBissextile occurrence
LEAPDAYIntercalary 24 hours for February.
LEAPDAYWhen Rossini was born in 1792
LEAPDAY2-29
LEAPDAYCalendrical correction
LEAPDAYFebruary 29th
LEAPDAYQuadrennial occurrence, mostly
LEAPDAYQuadrennial event
LEAPDAYQuadrennial occurrence
LEAPDAYCalendar rarity
LEAPDAYFebruary 29
LEAPDAYIntercalary event
LEAPDAYTraditionally, when women were allowed to propose marriage
LEAPDAY2004 event