According to the Bulgarian calendar, which is the oldest in the world, we are celebrating the year 7521. In 1976 UNESCO declared the ancient Bulgarian calendar as the most accurate in the world. Recent studies show that the beginning of the calendar dates back as early as 5505 BC. With its 12-year cycle it is similar to the Chinese calendar but is more ancient and most likely has served as its source. It is one of the oldest in the world.
The Mayan calendar, which has grown so popular, dates back only to the IX - X century.
According to the proto-Bulgarian calendar the year had 365 days. It started on the shortest winter day, which was celebrated as a holiday. Every fourth year there was one additional day, the so called “Day of the Sun” (in a leap year). The twelve months were formed by four quarters whereas the last month of each quarter had 31 days and the remaining two months – 30 days.