Lunar Cycle, Or Metonic Cycle, a period of 19 solar years, containing 235 lunar months and 6,940 days. This astronomical period was adopted by the Greeks in 432 B. C, at the motion of Meton and Euctemon, but it is a matter of doubt whether they were its inventors. It was the first exact calendar in general use, and in using the moon for measuring months nothing could be better. The calendar was, according to Ideler, as follows:

MONTHS.

YEAR OF THE CYCLE.

I.

11.

111.

IV.

v.

VI.

VII.

VIII.

IX.

X.

XI.

XII.

XIII.

XIV.

XV.

XVI.

XVII.

XVIII

XIX.

Hecatombaeon.........

30

29

30

30

30

30

29

30

30

30

29

29

30

30

30

29

29

30

30

Metageitnion.......

30

30

29

29

30

29

30

29

29

29

30

30

29

29

29

30

30

29

29

Boedromion............

29

29

30

30

29

30

29

30

30

30

29

29

30

30

30

29

29

30

30

Pyanepsion..........

30

30

29

29

30

30

30

29

29

30

30

30

29

29

29

30

30

29

30

Maemacterion.........

29

29

30

30

29

29

29

30

30

29

29

29

30

30

30

29

29

30

29

Poseideon.........

30

30

29

29

30

30

30

29

29

30

30

30

29

29

30

30

30

29

30

Poseideon II. (in leap years)

......

....

30

....

29

......

......

30

.....

......

30

.....

30

...

......

29

.....

.......

29

Gamelion...........

29

30

29

30

30

29

29

29

30

29

29

29

29

30

29

30

29

30

30

Anthesterion.........

30

29

30

29

29

30

30

30

29

30

30

30

30

29

30

30

30

29

29

Elaphebolion........

29

30

30

30

30

29

30

29

30

29

29

29

29

30

29

29

29

30

30

Munychion........

30

29

29

29

29

30

29

30

29

30

30

30

30

29

30

30

30

29

29

Thargelion..........

29

30

30

30

29

29

30

29

30

29

29

30

29

30

29

29

29

30

30

Sciorphorion..........

30

29

29

29

30

30

29

30

29

30

30

29

30

29

30

30

30

29

29

Number of days in a year...

355

354

384

354

384

355

354

384

354

355

384

354

384

354

355

384

354

354

384

In this manner the differences from the exact periods of the celestial bodies are everywhere reduced to a minimum, and at the end of the cycle there is a difference of only +9 hours 35 minutes from 19 solar years, and of 7 hours 29 minutes from 235 lunar months. Calippus attempted to overcome these inaccuracies by taking four Metonic cycles, and omitting one day in the fourth, which rendered his calendar similar to the subsequent Julian calendar. With this correction the lunar cycle is the best calendar except the Gregorian, over which it has the advantage that each month agrees with the cycle of phases within less than a day. The lunar cycle was in use in Greece, Macedonia, Asia Minor, and other countries. The Jews also adopted it, but they changed the leap years to the 3d, 6th, 8th, 11th, 14th, 17th, and 19th years of the cycle, and introduced a Veadar after Adar, or the sixth month. - See Madler, Ge-schichte der Himmelshunde (Brunswick, 1873).