noun
Autumnal Equinox Day
A Japanese national holiday around September 22–24, traditionally a time to honor ancestors and visit family graves.
秋分の日は、お墓参りに行く人が多い。
On Autumnal Equinox Day, many people visit their family graves.
The spring counterpart, Vernal Equinox Day, also a national holiday.
From 秋分 (autumnal equinox) + の (possessive particle) + 日 (day). The holiday was established in 1948 as a day to honor ancestors and remember the deceased.