also: ひととし · ひととせ
noun
one year; a year
Standard noun for a period of one year. The gloss 'some time ago' reflects a rare, context-dependent use where 一年 can mean 'a year or so ago' in informal speech, but this is not the primary meaning.
一年は三百六十五日です。
One year is 365 days.
彼は一年間日本に住んでいた。
He lived in Japan for one year.
Compound of 一 (いち, 'one') and 年 (ねん, 'year'). The readings ひととし and ひととせ are native Japanese readings of the same kanji, now largely obsolete.