A team of astronomer gumshoes has pinned down the date of an ancient Greek battle at Marathon that led to a long-distance run and the sport that survives today in its honor.

Analysis of lunar records show the 490 B.C. battle occurred not on the long accepted date of September 12, but a full month earlier, researchers said.

How important is a month for a professional runner more than 2,000 years ago? Apparently it's a matter of life and death.

According the Greek historian Herodotus, Plutarch and others, after the Greek army routed their Persian attackers at Marathon the long-distance runner Pheidippides sprinted the 26 miles (46 kilometers) back to Athens to announce the victory and warn of an attack from the sea, He then collapsed and died.

Having the run occur in August "makes it a little more plausible that he keeled over and died," said physics lecturer Russell Doescher, who worked on the study with team leader Donald Olson and colleague Marilynn Olson at Texas State University at San Marcos.

Temperatures in August can reach 102 degrees Fahrenheit (38 degrees Celsius) along the Marathon route, which could lead to heat exhaustion or heat stroke in even the hardiest of athletes, researchers said. The average temperature of the route in mid-September is about 83 degrees Fahrenheit (28 degrees Celsius), a time when thousands of amateur runners successfully complete the run with non-fatal results.

"Because [the event] happened so long ago, there’s been a lot of confusion and debate about when it actually occurred," Doescher told SPACE.com.

The research, which is detailed in the September issue of Sky & Telescope, is especially relevant to the upcoming 2004 Olympic games, where long-distance runners will retrace the famous trek on Aug. 29. That marathon, however, will start at 6:00 p.m. local time after the day’s peak temperatures.

"I’m actually going to be paying attention to the marathon event in the Olympics now," Doescher said.

According to Olson, the Greek historian Herodotus provided precise descriptions of the phase of the moon in his account of the battle, a key tool used by later investigators to time the event.

But researchers now believe the Sept. 12 date originally set by German scholar August Boeckh in the 19^th century, based on the Athenian lunar calendar, overlooked the importance of nearby Sparta.

Olson said the time of the Marathon battle and fatal run depends heavily on an earlier recorded trek by Pheidippides, when Athens city leaders dispatched the messenger to Sparta -- 150 miles (241 kilometers) away -- to plead for assistance in the defense of Greece. The Spartans promised help, though their army could not march until the next full moon six days away due to a religious festival.

Boeckh assumed the festival was Karneia in the Spartan month of Karneios, when warfare was prohibited for a week, then jumped to the Athenian calendar using previous connections between the two and determined the September date.

But the analysis, Oslon contends, should have been conducted wholly in Spartan lunar calendar, which -- although similar to the moon-based Athenian system -- began later in the year at the first new moon after the fall equinox. There were also 10 new moons instead of the typical nine separating the fall equinox of 491 B.C. and the summer solstice of 490 B.C., which caused the Spartan calendar to run a month ahead of Athens and led researchers to believe the Greek-Persian battle occurred in August.

Researchers said that while they had detailed accounts of lunar phases and dates of the Marathon battle by historians and ancient scholars, there were little Spartan records to rely on. Even those historians were themselves writing about history.