The two systems were to run on a trial basis for six months; early television sets supported both resolutions. However, the Baird system, which used a mechanical camera for filmed programming and Farnsworth image dissector cameras for live programming, proved too cumbersome and visually inferior, and ended with closedown (at 22:00) on Saturday 13 February 1937. 
Is there an answer to this question (If it cannot be answered, say "unanswerable"): How long did two systems run on a trial basis for?
unanswerable