Samurai zlash!

It's a Sep. calendar.

September 17 is Keirou no Hi (Respect for the Aged Day) in Japan this year.
Keirou no Hi is third Monday in September each year.
Keirou no Hi is holiday.

September 23 is Shuubun no Hi (Autumnal Equinox Day) in Japan this year.
Shuubun no Hi is decided on the Japanese Government.
Shuubun no Hi is sunday.

September 24 is holiday.
That day is Furikae Kyujitsu (substitute holiday) because Shuubun no Hi is sunday.

Ref.
-Keirou no Hi - Wikipedia (in Japanese)
-Shuubun no Hi - Wikipedia (in Japanese)
-Furikae Kyujitsu - Wikipedia (in Japanese)

By the way...
I feel that white Lisa's pose is Nandeyanen!

Nandeyanen means "Why? You are in fault.".
This word is popular in Japanese comedy.