当日

• Pinyin: dāng rì
• Hanzi breakdown: 当 = that, corresponding; 日 = 日 (sun, day)

Meaning

That day; the same day; on the day in question. Refers to a specific day already established in context.

Used in formal writing, legal documents, and journalism to refer back to a specific date already mentioned in the narrative. More formal than 当天, which is more colloquial.

Examples

1. 合同签订当日，双方代表均在场见证。 On the day the contract was signed, representatives from both sides were present to witness it.
2. 事故发生当日，警方迅速封锁了现场并展开调查。 On the day of the accident, the police quickly sealed off the scene and launched an investigation.
3. 当日抵达的旅客须在指定窗口完成入住登记手续。 Travelers arriving that day must complete check-in procedures at the designated counter.

Usage Guide

Context: legal, journalism, official records

Tone: neutral

Do Say

• 票务规定显示，当日购票当日有效，不得延期使用。(Ticketing rules state that tickets purchased on that day are valid only on that day and may not be deferred.)
• 当日的会议记录已整理归档，供各部门查阅。(The meeting minutes from that day have been filed and archived for departmental reference.)

Don't Say

• 我当日要去 — 当日 refers to a day established in context, not today; use 今天 or 今日 for the current day

Origin & History

当 (that, on that) + 日 (day)

Cultural Context

Generation: All ages

Social background: Universal