noun
The first month of the Gregorian calendar. Used in dates, schedules, and everyday references.
一月は一年で一番寒い月です。
January is the coldest month of the year.
彼の誕生日は一月十五日
His birthday is January 15th.
noun
first month of the lunar calendar
Refers to the first month in the traditional Japanese lunar calendar, roughly corresponding to February in the modern calendar. Used in historical or cultural contexts.
旧暦の一月は、今の二月ごろにあたります。
The first month of the old lunar calendar corresponds to around February now.