Akagis modernization was completed on 31 August 1938. She was reclassified as a first reserve ship on 15 November, but did not rejoin the First Carrier Division until the following month. In her new configuration, the carrier embarked 12 Mitsubishi A5M Type 96 "Claude" fighters with 4 disassembled spares, 19 Aichi D1A "Susie" dive bombers with 5 spares, and 35 Yokosuka B4Y "Jean" horizontal/torpedo bombers with 16 spares. She sailed for southern Chinese waters on 30 January 1939 and supported ground operations there, including attacks on Guilin and Liuzhou, until 19 February, when she returned to Japan. Akagi supported operations in central China between 27 March and 2 April 1940. She was reclassified as a special purpose ship (Tokubetse Ilomokan) on 15 November 1940, while she was being overhauled.
Question: What months after modernization was complete did Akagis rejoin the First Carrier Division?
Answer: December 1938