Merry Christmas, all over again

For much of the world Christmas Day is on December 25 but many countries celebrate it on January7.

This is because some countries use a calendar different to that used in the West, the Gregorian, proposed by Pope Gregory in 1582.

But much of the former Soviet Union and the Middle East uses the Julian calendar, introduced by Roman emperor Julius Caesar in 45 BC.

Germany did not adopt the Gregorian calendar until 1775; Bulgaria not until 1917.

Nowadays most countries use the Gregorian calendar but some retain the Julian to demarcate their traditional holiday.

There is a 13-day discrepancy between the two calendars.

"December 25 on the Julian calendar is January 7 on the Gregorian," explained Christopher Calin, dean of the Russian Orthodox Cathedral of the Holy Virgin Protection, in New York.

"Christmas is still on December 25 - but it just happens to fall 13 days later on the Julian calendar."