Given the task definition and input, reply with output. Generate a correct and concise answer for the question based on the words in the context.

Context : At FCM Jammy and Savatier finished the Char 2C prototype, the other nine tanks being built almost simultaneously; all ten were delivered in 1921 and modified by the factory until 1923.
Question : In which year was the service entry date for Char 2C?
1921