(名詞) 一個人出生第 10,000 天。亦寫成 10K day

當你出生第 10,000 天時,你的年紀大約是 27 歲又 3 個月 15 天。

Approaching his tkday — or 10,000th day on Earth — Horne decided he wanted to leave a permanent mark on history, and as a lover of language and devout Countdown fan, he decided that the best way to do that would be to get a new word into the dictionary.
—Steve Bennett, "Wordwatching by Alex Horne," Chortle, January 14, 2010

The 10k Day celebration — alternately called "Tkday" or "decimal birthday" — has become the new coming-of-age for Generation Y.
—Paola Loriggio, "Happy 10,000th day — let's party," The Toronto Star, February 23, 2008