Claim: The summer transfer window, which is the period during the year in which a football club can transfer players from other playing staff into their playing staff. that opened on 1 July 2015 and ended on 1 September 2015.
Evidence: A transfer window is the period during the year in which a football club can transfer players from other playing staff into their playing staff. Most major European leagues commence in the second half of the year (e.g. August or September) and stretch over two calendar years to the first half of the next year (e.g. May), resulting in a close season window in the Summer ending in August, and a mid-season window in January.