某ぼう日じつ

noun, adverb

a certain day; one day

Used when the specific date is not named, often in narratives, announcements, or formal writing. Functions as a noun or adverbially.

• 某ぼう日じつ、都と内ないのホテルで会かい合ごうが開ひらかれた。

  On a certain day, a meeting was held at a hotel in Tokyo.

• 事じ件けんは某ぼう日じつ午ご後ご３時じごろ発はっ生せいした。

  The incident occurred around 3 p.m. on a certain day.