also: なぬか
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.
seven days
Used for a period of seven days; less common than 一週間 in everyday speech.
七日間の旅行を計画している。
I'm planning a seven-day trip.
My birthday is April 7th.
It takes seven days to finish this work.
The results will come out seven days later.