I thought my capacity for sheer jaw-dropping amazement at the Antikythera mechanism had been well and truly exhausted – until last night. The puzzling instrument is a clockwork computer from ancient Greece that used a fiendishly complex assembly of meshed cogs to simulate the movement of the planets, predict lunar eclipses and indicate the dates of major sporting events.

The clockwork technology in the device was already known to be centuries ahead of its time, but new evidence suggests that the enigmatic machine is even older than scientists had realised. "It is the most important scientific artefact known from the ancient world," said Jo Marchant, who has written a compelling book on the find called Decoding the Heavens. "There's nothing else like it for a thousand years afterwards."

First, a quick recap. The Antikythera mechanism was discovered by sponge divers in 1901 who chanced upon the wreck of a Roman vessel off the coast of the Greek island of Antikythera. The ship was filled with bronze statues, pottery and glassware – booty that had been plundered from across the ancient Greek world.

At first no one noticed the corroded lump of cogs among the treasures, but the mechanism has since attracted the, at times, obsessive interest of a small group of scientists. What we now know about the mechanism and its purpose is a fascinating tale of scientific rivalry, low-down skulduggery and eventual glory.

There is much still to learn about where the machine came from, who made it and what it was for, but the best guess seems to be that it was more must-have executive toy than useful gadget. It modelled the state-of-the-art astronomy of the time: a universe with the Earth at the centre with planets following circular orbits that included apparent wobbles called epicycles.

The mechanism was probably not used for navigation but perhaps served more as a beautiful representation of an ordered, clockwork universe. "Something to elevate the spirit and get closer to God or the true meaning of things," as Marchant put it during a talk at the Royal Institution in London last night.

So what about the new stuff? Research from Prof Alexander Jones of the Institute for the Study of the Ancient World, New York, which has yet to be published, suggests that rather than dating from the 1st century BC the Antikythera mechanism may in fact have been constructed in the preceding century.

The new data concerns the four-year Olympiad dial, which has the names of significant Greek games etched into it – Isthmia, Olympia, Nemea, Pythia and Naa (plus one other that hasn't been deciphered). The first four were major games known throughout the ancient world, but the Naa games, held near Dodona in northwest Greece, were a much more provincial affair that would only have been of local interest. "One possibility is that it was made by or for somebody in Naa," said Marchant, who described the clockwork computer on the Guardian's Science Weekly podcast last year.

This also helps to pin down the date because the Romans took over that region in the 2nd century BC. A Greek-inscribed gadget like this, reasons Jones, would not have been made after the Romans took charge.

The highlight of Marchant's talk, though, was a new animation of the Antikythera device that brings it to life like nothing I have seen before. "That's one of my favourite things at the moment," said Marchant as the packed audience at the Royal Institution broke into spontaneous applause after watching the animation in stunned silence. I think I agree.

Jo Marchant's book Decoding the Heavens will be published in paperback on 6 August. It is among the six books shortlisted for this year's Royal Society Science Book Prize