月旦
げ
っ
た
ん
Meanings
1
Literary or formal term for the first day of a month; in modern Japanese 一日 (ついたち) is far more common.
There is a custom of visiting a shrine on the first day of the month.
2
character sketch; commentary on personalities
abbreviation
Abbreviation of 月旦評 (げったんひょう); a classical Chinese-derived term for evaluating people's character. Rare in modern Japanese outside historical or literary contexts.
See also: 月旦評
He was good at character sketches.