also: じゅうななにち
noun
17th day of the month
Refers to the 17th day of any month. The reading じゅうしちにち is more common than じゅうななにち.
会議は１７日に行われます。
The meeting will be held on the 17th.
noun
17 days
Indicates a duration of seventeen days. Often used with counters or in time expressions.
このプロジェクトは１７日かかりました。
This project took 17 days.