Quadrennial occasion celebrated by this puzzle's theme entries

Question:

Answer:

LEAPDAY

Length:

Similar Crossword Questions:

The three of this puzzle's theme entries
Physical principle whose equation explains the changes in this puzzle's theme entries
What this puzzle's theme entries probably do?
Like some fillings (as in this puzzle's theme entries)
Find new work - or what you must do to get the three theme entries' names in this puzzle
First of a pair of letters swapped six times in this puzzle's theme entries
Challenged, or what the theme entries in this puzzle should be
They're hidden in this puzzle's theme entries
This puzzle's theme entries
Event celebrated in this puzzle, and an example of how the theme works
Second of a pair of letters swapped six times in this puzzle's theme entries
What the constructor had to do to create the theme entries in this puzzle (boyeee)
This puzzle's theme entries, e.g.
What the three theme entries in this puzzle are, in either of two ways
Playoff series finale ... or an apt title for this puzzle considering the number and length of its theme entries
What this puzzle's theme entries are
Office building problem that's a hint to this puzzle's theme entries (see their last three letters)
Many people get one in the summer (and so do this puzzle's theme entries)
Word that has two diametrically opposed meanings (like this puzzle's eight theme entries)
"Lid" in each of this puzzle's theme entries
Activity suggested by this puzzle's theme entries
December 21, and the occasion for this puzzle's theme
Levels that are split in this puzzle's theme entries
Just making things up, or a synonym for a three-word phrase describing this puzzle's theme entries
The three in each of this puzzle's theme entries