Metonic cycle

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Metonic cycle:

see synodic periodsynodic period
, in astronomy, length of time during which a body in the solar system makes one orbit of the sun relative to the earth, i.e., returns to the same elongation.
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Metonic cycle

(me-ton -ik) (lunar cycle) A period of 19 years (tropical) after which the phases of the Moon recur on the same days of the year: the period contains 6939.60 days, which is very nearly equal to 235 synodic months, i.e. 6939.69 days. Since it is also almost equal to 20 eclipse years, i.e. 6932.4 days, it is possible for a series of four or five eclipses to occur on the same dates at intervals of 19 years. The cycle was discovered by the Greek astronomer Meton in the fifth century bc and was used in determining how intercalary months could be inserted into a lunar calendar so that the calendar year and the tropical (seasonal) year were kept in step.
Collins Dictionary of Astronomy © Market House Books Ltd, 2006

Metonic Cycle

(religion, spiritualism, and occult)

The ancient Greek Meton discovered that the Moon has a cycle of 19 years, after which a new moon occurs on the same day of the year.

The Astrology Book, Second Edition © 2003 Visible Ink Press®. All rights reserved.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Metonic Cycle


a time interval of 6,940 days used for bringing into agreement the length of a lunar month and solar year in a lunisolar calendar. It was proposed in 433 B.C. by the Athenian scholar Meton and was the foundation of the ancient Greek calendar. The Metonic cycle is related to the approximate (to within several hours) equation 19 tropical years = 235 synodic months. The Metonic cycle contains 19 years—12 years of 12 months each and seven years of 13 months each. Out of these 235 months, 125 months are called full months, that is, they have 30 days each, and the remaining 110 months are called hollow months and have 29 days each. The Metonic cycle is also used in the Jewish and ancient Christian calendars.

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.

metonic cycle

[me′tän·ik ′sī·kəl]
A time period of 235 lunar months, or 19 years; after this period the phases of the moon occur on the same days of the same months.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.