also: なぬか
noun
7th day of the month
Refers specifically to the seventh day of a calendar month.
会議は来月の七日です。
The meeting is on the 7th of next month.
I'm planning a seven-day trip.
一週間 is the standard word for 'one week' or 'seven days' in modern Japanese; 七日 is more formal or literary for the duration.
Compound of 七 (nana, 'seven') and 日 (ka, 'day'), with a euphonic change from nana-ka to nano-ka. The reading なぬか is an older form.