Changsub's mandatory military service summons date is January 14, 2019. The idol will reportedly answer to the date above, and enlist as an active duty soldier after carrying out his basic training.
[UPDATE:] Cube Entertainment confirmed to media outlets shortly after the exclusive report, that Changsub will enlist on January 14. There will be no official ceremony and the idol will enlist quietly.
Meanwhile, Changsub's 1st mini album 'Mark' is set for release this December 11.