Shuubun no hi 秋分の日 9/23
and OHIGAN お彼岸 9/20~26
9/23 day time = night time (almost same time, not exactly same time)
so, this day is called "Shuubun no hi" in Japan
it starts autumn
before 3days 9/23 and after 3days 9/23 = 9/20 ~ 26 called OHIGAN
Buddist custum
"祖先を敬い、亡くなった人々を偲ぶ"
(sosen wo uyamai , nakunatta hitobito wo shinobu)
by wikipedia
"the term for respect ancestors and recall the deceased"
this means for generally "haka mairi""墓参り" (a day for visit to a grave. only in japan)
and eat OHAGI!
OHAGI おはぎ