THE DATES USED IN THIS BOOK FOLLOW THE OLD-STYLE JULIAN CALENDAR IN USE IN RUSSIA UNTIL FEBRUARY 1918. IN THE NINETEENTH CENTURY THAT CALENDAR LAGGED TWELVE DAYS BEHIND THE GREGORIAN CALENDAR USED IN THE WEST; IN THE TWENTIETH, IT LAGGED THIRTEEN DAYS BEHIND. NICHOLAS AND ALIX USED A DOUBLE-DATING SYSTEM IN THEIR DIARIES AND LETTERS BEGINNING IN FEBRUARY 1918, BUT NICHOLAS SOON RETURNED TO THE OLD-STYLE DATING.