also: つごもり · みそ · かいじつ
noun
last day of the month; month-end day
A noun for the final day of any month. In ordinary modern speech 月末 is more common for 'the end of the month'; 晦日 and especially つごもり have a more traditional or literary feel. 十二月の晦日 is 大晦日, New Year's Eve.
See also: 月末
毎月の晦日に帳簿を締める。
We close the books on the last day of every month.
十二
The last day of December is called Ōmisoka, New Year's Eve.
Attested older or literary reading for 晦日.
Rare Sino-Japanese-style reading of 晦日; not the normal everyday reading.
Older short kanji spelling with the reading つごもり; mainly useful for literary or historical texts.
Rare attested reading of 晦; included mainly to help recognize or search unusual spellings.
The common everyday word for the end of the month; 三十日／晦日 specifically means the final day itself and can sound more traditional.
A more formal word for the last day of a month, period, or deadline; often used in business or official contexts.
Specifically the last day of the year, December 31; it contains 晦日 but is a separate fixed word.
みそか is associated with 三十日, literally 'thirtieth day'; historically the last day of a month was tied to a roughly thirty-day month. 晦日 and 晦 are conventional kanji spellings connected with the month's end. The exact historical development is summarized cautiously here rather than treated as a fully verified etymology.