Bulgarians bring over from millennia before Christ one of the most perfect systems for measuring the duration of the year on earth. The movement of the constellations, represented as animals, forms a 12-year cycle, in accordance with the route of Yankul (Jupiter) around the Sun.
THE SIGN OF THE CALENDAR is a CROSS WITH EQUAL ARMS, the images of the Sun and Jupiter situated between its upper arms.

THE CROSS is a universal image from time immemorial, symbolizing the bond between Heaven and Earth. It is structured by the rules of the calendar. On the day of the spring and autumn equinox (March 22 and September 22) the shadows cast by the vertical axis represent the two equal horizontal arms of the cross. On the days of the summer and winter solstice (June 22 and December 22) the shadows represent the vertical short and the long arms of the cross.

The Beginning of the Ancient Bulgarian Chronology It is known that the ancient Bulgarians knew perfectly well the basic laws of motion of the planets and the Earth around the Sun and because of that they possessed one of the most impeccable calendars ever. The calendar of the ancient Bulgarians surpassed the Indian and the Chinese calendar systems in the way the days and months were arranged. According to the ancient Bulgarian calendar, the year had 365 days. It began with the shortest winter day, which was a holiday. An extra day, called “The Day of the Sun” was added to every 4th year.
The shortest winter day and the Day of the Sun were not to be on a Sunday. Twelve months formed four quarters, the first month of the quarter having 31 days and the other two months having 30 days. Thus, every member of the ancient Bulgarian community was able to keep track of time independently.
In the ancient Bulgarian chronology, there were periods of 3, 10, 12, 17, 19, 21, 30, 47, 50, 53, 300, 600, 4332, etc. ancient Bulgarian years which were used both as denominators and intervals of time.

The longest one was of 6328 ancient Bulgarian years. It is mentioned in the fragmentary inscription of Khan Omurtag and refers to the year 823 AD. The text consists of 14 lines, probably the concluding part of a contract between Danube Bulgaria and Byzantium. The inscription is carved with beautiful letters in a marble stone most probably from the capital town of Pliska*. Here is what it says:
In the ancient Bulgarian chronology, there were periods of 3, 10, 12, 17, 19, 21, 30, 47, 50, 53, 300, 600, 4332, etc. ancient Bulgarian years which were used both as denominators and intervals of time. The longest one was of 6328 ancient Bulgarian years. It is mentioned in the fragmentary inscription of Khan Omurtag and refers to the year 823 AD. The text consists of 14 lines, probably the concluding part of a contract between Danube Bulgaria and Byzantium. The inscription is carved with beautiful letters on a marble stone most probably from the capital town of Pliska*. Here is what it says:
“[…of the ruler] the name is [Khan Omurtag Juvigi]. The year of the appearance of the true god was 6328. They made a sacrifice and they swore in the written in the books [mutual contracts]…”
This historic source may be accepted as a proof of the early beginning of the chronology of the Bulgarian calendar. According to the counts of the great Bulgarian historian Professor Vassil Zlatarski the beginning is the year 5505 BC. Therefore, we can calculate that the new year, 2001 AD, is the year 7506 of the ancient Bulgarian chronology. Thus, the Bulgarians are among the peoples with the most ancient system of measuring time – a fact, which indicates their early civilising force.

Academician D. Mishev, Bulgarian Academy of Sciences