The climata were the ancient divisions of the inhabited portion of the spherical Earth

Spherical Earth

The concept of a spherical Earth dates back to ancient Greek philosophy from around the 6th century BC, but remained a matter of philosophical speculation until the 3rd century BC when Hellenistic astronomy established the spherical shape of the earth as a physical given...

 by parallel circles centered on the Pole. The word stems from the Greek

Greek language

Greek is an independent branch of the Indo-European family of languages. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. Its writing system has been the Greek alphabet for the majority of its history;...

 κλίμα, Latin

Latin

Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 clima, terms which are originally geometric in nature, κλίμα meaning inclination or slope of the ground.

Historical Development

The climata were defined by the length of the longest daylight, and were further associated with specific geographical locations. There were seven classical climata, although in his Almagest

Almagest

The Almagest is a 2nd-century mathematical and astronomical treatise on the apparent motions of the stars and planetary paths. Written in Greek by Claudius Ptolemy, a Roman era scholar of Egypt,...

 Ptolemy

Ptolemy

Claudius Ptolemy , was a Roman citizen of Egypt who wrote in Greek. He was a mathematician, astronomer, geographer, astrologer, and poet of a single epigram in the Greek Anthology. He lived in Egypt under Roman rule, and is believed to have been born in the town of Ptolemais Hermiou in the...

 gave a more extensive listing of 39 climata, from which the following excerpt is tabulated:

Clima	Longest Daylight	Location	Latitude
	12 hours	Equator	0°
I	13 hours	Meroe Meroë Meroë Meroitic: Medewi or Bedewi; Arabic: and Meruwi) is an ancient city on the east bank of the Nile about 6 km north-east of the Kabushiya station near Shendi, Sudan, approximately 200 km north-east of Khartoum. Near the site are a group of villages called Bagrawiyah...	16°27'
II	13½ hours	Syene	23°51'
III	14 hours	Lower Egypt Lower Egypt Lower Egypt is the northern-most section of Egypt. It refers to the fertile Nile Delta region, which stretches from the area between El-Aiyat and Zawyet Dahshur, south of modern-day Cairo, and the Mediterranean Sea....	30°22
IV	14½ hours	Rhodes Rhodes Rhodes is an island in Greece, located in the eastern Aegean Sea. It is the largest of the Dodecanese islands in terms of both land area and population, with a population of 117,007, and also the island group's historical capital. Administratively the island forms a separate municipality within...	36°
V	15 hours	Hellespont	40°56'
VI	15½ hours	Mid-Pontus Pontus Pontus or Pontos is a historical Greek designation for a region on the southern coast of the Black Sea, located in modern-day northeastern Turkey. The name was applied to the coastal region in antiquity by the Greeks who colonized the area, and derived from the Greek name of the Black Sea: Πόντος...	45°1'
VII	16 hours	Mouth of Borysthenes Borysthenes Borysthenes is a geographical name from classical Antiquity. It usually refers to the Dnipro River, but occasionally to the Pontic Olbia, a town situated at the mouth of that river. The Borysthenes is mentioned numerous times in 'The History of the Decline and Fall of the Roman Empire' by Edward...	48°32'
	17 hours	Mouth of Tanais Tanais Tanais is the ancient name for the River Don in Russia. Strabo regarded it as the boundary between Europe and Asia.In antiquity, Tanais was also the name of a city in the Don river delta that reaches into the northeasternmost part of the Sea of Azov, which the Greeks called Lake Maeotis...	54°1'
	18 hours	South of Little-Britain	58°
	19 hours	North of Little-Britain	61°
	20 hours	Thule Thule Thule Greek: Θούλη, Thoulē), also spelled Thula, Thila, or Thyïlea, is, in classical European literature and maps, a region in the far north. Though often considered to be an island in antiquity, modern interpretations of what was meant by Thule often identify it as Norway. Other interpretations...	63°
	21 hours	Unknown Skythians	64°30'
	22 hours		65°30'
	23 hours		66°
	24 hours		66°8'40"
	2 months		69°30'
	4 months		78°20'
	6 months	North Pole	90°

In Medieval Europe

Middle Ages

The Middle Ages is a periodization of European history from the 5th century to the 15th century. The Middle Ages follows the fall of the Western Roman Empire in 476 and precedes the Early Modern Era. It is the middle period of a three-period division of Western history: Classic, Medieval and Modern...

, the climates for 15 and 18 hours were used to calculate the changing length of daylight through the year.