14th January, 2014, is new year according to the Eastern Orthodox church, or some of them, which has kept the Julian calendar – or a version of it – instead of taking on the Gregorian calendar, which was introduced in 1582.
The Julian calendar had been introduced by Julius Caesar and added the leap year to make up 0.25 of a day each year was out. But the year was actually out by 0.2425 of a day, ie, slightly LESS than a quarter of a day. By the 1500s this meant the calendar was out by 10 days, and more importantly, meant Easter, which was meant to be celebrated at the time of the Spring equinox, was out, and so the reforms were brought in.
But while Catholic countries took it up quickly (as Gregory was the Pope) Protestant and Orthodox countries were suspicious of it. It wasn’t taken up in England until 1752.
The Orthodox churches didn’t take it up within their church, although the countries did slowly adopt it as their civil calendar. Russia took it up finally in 1918 (ie, after the revolution) and Greece did not take it up until 1923. That’d be right, the Greeks never did like the Romans.
While most countries in the world have taken it up, some still have not, including – according to Wikipedia – Saudi Arabia, Ethiopia, Nepal, Iran and Afghanistan