Conversation so far:
Did Bill Shankly play or manage for Carlisle?
Shankly began his managerial career at the club.
When did he become manager?
1948-49 season.
How did he do in his first season?
Shankly's work ethic transformed the team who finished 15th in 1948-49 after he had been in charge for only the last few matches.
Did he make any big changes to the team?
Shankly used psychology to motivate his players.
Did he bring in any new players?
Geoff Twentyman, then a promising young centre half, who was later transferred to Liverpool.
How long did he manage Carlisle?
Shankly resigned and took up an offer from Grimsby Town.

Question: When did that happen?
Self-contained rewrite: When did Shankly manage Carlisle United?