also: じょうにち · じょうじつ
noun
Refers to a predetermined or scheduled date, often used in formal or administrative contexts such as payment deadlines, meetings, or legal appointments.
会議の定日は毎月第一月曜日です。
The fixed date for the meeting is the first Monday of every month.
支払いの定日を過ぎると延滞料金がかかります。
If you miss the appointed payment date, a late fee will be charged.
Alternate reading; less common than ていじつ.
期日 (きじつ) also means a fixed date or deadline, but is more common and broader, often used for due dates and time limits. 定日 is more formal and emphasizes a regularly scheduled or predetermined day.
日程 (にってい) refers to a schedule or itinerary, focusing on the overall plan of events, while 定日 specifically means a single fixed day.
Compound of 定 (てい, 'fixed, determined') and 日 (じつ, 'day'). The reading ていじつ is the standard on'yomi combination. Alternate readings じょうにち and じょうじつ are less common and may reflect older or dialectal variations.