Once again, there's a piece of information missing here – although to be fair it's not as crucial as the previous one.
The question should have asked in what decade the Gregorian calendar was introduced in Great Britain.
The Gregorian calendar was introduced in Venice, France, Spain, Portugal and the Netherlands in 1582, and in the Catholic states of the Holy Roman Empire the following year. The Protestant states of the Holy Roman Empire converted in 1700, and it was in 1752 that Great Britain followed suit.
Sweden followed one year later (1753), and Russia in 1918.
Most people would no doubt have guessed that it was the British date that we were looking for. But this is no excuse for the question setter's omission.
© Macclesfield Quiz League 2018