Day rose to the top of his profession during the reign of Edward VI (1547–1553). At this time, restrictions on publishers were relaxed, and a wave of propaganda on behalf of the English Reformation was encouraged by the government of the Lord Protector, Edward Seymour, 1st Duke of Somerset. During the reign of the Catholic Queen Mary I, many Protestant printers fled to the continent, but Day stayed in England and continued to print Protestant literature.