BeiDou Navigation Satellite System:

The first satellite, BeiDou-1A, was launched on October 31, 2000. The second satellite, BeiDou-1B, was successfully launched on December 21, 2000. The last operational satellite of the constellation, BeiDou-1C, was launched on May 25, 2003.

Please answer a question about this article. If the question is unanswerable, say "unanswerable". When was the second satellite for the BeiDou-1 system launched?
December 21, 2000