In 1752, Britain changed its calendar from the old “Julian” style to the Gregorian version that most of Europe was already using. People rioted, demanding back the 11 days of their lives that had gone “missing” in the switchover, but there would be far-reaching effects too. Any festivals set by the phases of the moon continued as ever, but set dates, such as Midsummer and Christmas, now fell on the “wrong” days. Plants didn’t know this, of course, but it muddled folklore, making some customs even stranger to modern eyes.