An academic claims to have discovered the world's oldest existing Babylonian calendar, which shows that the Jewish dating system has changed little in 2,000 years.

Dr Helen Jacobus, who was recently awarded PhD by Manchester University, is the first academic to decipher the document which was found with the Dead Sea Scrolls into a calendar capable of calculations.

The system predicts the position of the moon in the zodiac and concurs so closely with the dating system used by Jews today that it can still be used.

"The document is the earliest remnant of an ancient calendar that is close to the rabbinic calendar Jews use today," said Ms Jacobus, a former JC journalist.

"The fact that you can access this calendar through today's Jewish calender would suggest ours is a very close descendant. Nobody has reproduced a computer programme that can find the moon's position in this way. It's the only existing piece of software of its kind, if you like - it's remarkable."

Dr Jacobus's academic paper on the calendar won an award from the William F Albright Institute of Archaeological Research in Jerusalem.