What's odd Mandie? Do you mean the double dates, and then the difference after 1900? Until the Revolution, Russia used the Old Calendar (the Julian calendar), as did several other Orthodox countries. By the 1800s, this was 12 days behind the calendar which was used in Western Europe. England and America changed to the New Calendar (Gregorian) some time in the 1700s, many of the Catholic countries changed in the 1500s when Pope Gregory invented the new calendar (which is why the Protestant and Orthodox countries didn't take it on). In the 20th Century, the time difference between the calendars became 13 days (and it still is). As far as Olga was concerned, her birthday was always 3 November, but in the west, when she was a baby that day was 15 November, by the time she was 5 in the west the same day was 16 November. (Something to do with leap years in one system and not the other I think).
The Orthodox Church still uses the Old Calendar (some jurisdictions use the new for everything but Easter and associated feasts, but it is very hard to reconcile the dates and calendars, so for ecclesistical matters, IMHO it is best to use the old Calendar, the new one is fine for secular purposes.)
