An engraved stone carved around 10,000 years ago may be the world’s oldest example of a lunar calendar.

The rare pebble — found high up in the mountains near Rome, Italy — dates back to the Stone Age, experts claim.

Archaeologists first discovered the hammer-stone on top of Monte Alta in the Alban Hills in 2007.

But only now have the pebble’s secrets been unlocked, thanks to modern microscopic and macroscopic analysis techniques.

It’s believed that our early ancestors would’ve used the stone to keep track of the moon’s cycles — long before we could rely on an iPhone calendar app.

“The investigations have revealed that the notches have been inscribed over time using multiple sharp stone tools,” said Flavio Altamura, of Sapienza University of Rome, in the Journal of Archaeological Science.

These notches were engraved “as if they were being used to count, calculate or store the record of some kind of information,” Flavio added.

The long pebble has three separate series of notches.

And the sections have seven, nine or ten and eleven notches respectively.

These notches — which total either 27 or 28 — suggest the stone’s engraver used the pebble to track lunar cycles.

“Analyses made it possible to reconstruct the types and chronology of human intervention on the pebble,” said Flavio.

The archaeologist explained that “they were made over time using more than one kind of cutting edge” and that the pebble is “one of the few known cases of this kind in the world prehistoric record.”

“Moreover, it displays all the features theorized in literature for the validation of lunar calendars,” Flavio wrote.

“This could have significant implications for the reconstruction of the cognitive and mathematical ability of Homo sapiens in prehistoric times.”

It’s believed that the lunar calendar dates back to the Upper Paleolithic (or Old Stone Age) period, which ended around 10,000 years ago.

A lunar calendar is used to keep track of the monthly cycles of the moon’s phases.

That’s in contrast to solar calendars that are common today, which are based on the solar year of 365 days.

Lunar calendars vary on when the month begins, but each “lunation” period is consistent at around 29.5 days.

They were traditionally used in ancient times to determine festivals and holidays, as well as more generally to track the passage of time.

So how does the carved stone compare to other ancient lunar calendars in terms of age?

The previous oldest lunar calendar was found at Warren Field in Scotland and dates back to the Mesolithic period — around 8,000 BC.

Some archaeologists have suggested that earlier examples exist — from 15,000 BC and 25,000 BC — but the findings are controversial.