question: What designation was added to British dates to differentiate them from countries not using the new calendar ?
answer: `` Old Style '' ( OS ) and `` New Style ''
turker_answer: `` Old Style '' ( OS ) and `` New Style '' were added to British dates to differentiate them from countries not using the new calendar .
rule-based: `` Old Style '' ( OS ) and `` New Style was added to British dates to differentiate them from countries not using the new calendar .