How Greeks measured time and distance

Imagine life without a clock or a phone. The Greeks looked up instead. A new month, a μήν, began with the new moon, and anyone could see it. Farmers followed the stars: the poet Hesiod (Works and Days 615–617) tells them to remember the ploughing when the Pleiades, the Hyades and Orion set.

During the day, the clock was a shadow. An upright pointer, the γνώμων, cast a shadow that grew shorter towards noon and longer towards evening, and people gave its length in feet. In a comedy by Aristophanes (Assemblywomen 652), a man is told he will go to dinner “when the shadow is ten feet long”.

Herodotus (2.109) says that the Greeks learned the pointer and the twelve parts of the day from the Babylonians. The word ὥρα first meant a season or the right moment; the meaning “hour” came in the Hellenistic period. Those hours were not all equal. Daylight was divided into twelve parts, so a summer hour lasted longer than a winter one.

Twelve moon months of 29 or 30 days make about 354 days, some eleven days short of the Sun’s year. Left alone, festivals would drift through the seasons. So Athens sometimes added a thirteenth month, usually a second Ποσιδεών. The archon decided, apparently rather haphazardly, and in Aristophanes’ Clouds (615–626) the Moon herself complains that the Athenians get their days wrong. In 432 BC the astronomer Meton worked with a 19-year cycle, since 19 solar years come very close to 235 moon months. Modern accounts differ: some say he introduced it into the Athenian calendar, others only that he proposed it, and how far officials followed it is unclear.

Each city kept its own calendar. The treaty of 421 BC (Thucydides 5.19) gives its date twice: the month Ἀρτεμίσιος in Sparta and Ἐλαφηβολιών in Athens, with the last days counted down to the end of the month. Nor did years have numbers. Thucydides (2.2) dates the start of the war by a priestess at Argos, an ephor at Sparta and an archon at Athens, then (5.20) warns against such lists and counts summers and winters. Athens also ran a political year of ten πρυτανεῖαι, four of 36 days and six of 35 (Constitution of the Athenians 43.2).

Speakers in Athenian courts had a time limit, kept by the κλεψύδρα, the “water thief”: a jar with a narrow hole underneath. The Constitution of the Athenians (67.2), from Aristotle’s school, lists the allowance in χόες, a measure of liquid. The largest private cases, over 5,000 drachmas, got ten χόες, plus three for the second speech. Smaller cases got less.

A real one survives in fragments. Excavators in the Athenian Agora found a clay water clock of the late 5th century BC, marked ΧΧ for two χόες. It held about 6.4 litres and took about six minutes to empty. At that rate, ten χόες gave a speaker about half an hour.

Greeks also used the word ὡρολόγιον, “hour-teller”, for both sundials and water clocks. The Tower of the Winds in the Roman Agora of Athens had at least nine sundials and a large water clock, now lost. Its date is not recorded: proposals run from the 2nd century BC to about 50 BC. The same word gives the everyday ρολόι, which lost its first vowel along the way.

Length started with the body. Herodotus (2.149) gives the chain: a foot, πούς, is four palms and a cubit, πῆχυς, six palms. An ὀργυιά, the span of the outstretched arms, is six feet, and a hundred of them make a στάδιον, which equals six πλέθρα. So a stadion is 600 feet. For long journeys he adds the Persian παρασάγγης, 30 stadia (5.53).

These figures do not convert neatly into metres. The stadion was also a running race, and the Greek Ministry of Culture gives its length at Olympia as 192.28 m. The Triantafyllidis dictionary gives 180–200 m for the unit. Scholars still argue about the one Eratosthenes used when he measured the Earth: 157.2 m and 166.7 m have both been proposed.

The words live on, often by a side road. Πούς gave πόδι through its diminutive πόδιον, and στάδιο means a sports ground today under the influence of French stade, itself from the Greek. Μέτρον is still μέτρο, and the unit, the metre, came back from French mètre. The months did not survive: today’s Ιανουάριος comes from Latin Ianuarius, not from Athens.