23rd day of the month
Used for dates; the 23rd day of any month.
The meeting was postponed to the 23rd.
23 days
Used for a duration of 23 days. Less common than the date sense.
This project was completed in 23 days.
The meeting will be held on the 23rd.
This construction work took 23 days.
二十三日 (にじゅうさんにち) means the 23rd day of a month or a duration of 23 days, while 二三日 (にさんにち) means a vague 'two or three days' even though it can share the same kanji spelling.
Standard kanji spelling for the 23rd day of the month.
Arabic numeral spelling, very common in schedules and dates.
Rare variant; easily confused with 二三日 (にさんにち, 'two or three days').
Compound of 二十 (にじゅう, 'twenty'), 三 (さん, 'three'), and 日 (にち, 'day').