For our purposes it is more suitable luni-solar calendar, because – the solar year contains a fractional number of lunar months (around 12.37). To include solar year lunar months without them breaking up, added a lunar month every few years, bringing these lunar years for solar. These years contained elongated, hence, on 13 lunar months. This is the basic idea of lunar-solar calendar, which was thus a combination of lunar months with solar years. The existence of such a lunar-solar calendar in the ancient world is well known from the edicts of the Babylonian king Hammurabi (2067-2025 years. bc. Er.). Later in Babylon appeared lunar-solar calendar system.
The first of these was eight-year luni-solar cycle (oktaeterida). In an eight-year lunisolar calendar cycle included the 2922 days (8 x 354 + 3 x 30). In fact, eight solar years contain 365,242195 x 8 = 2921.94 days. As you can see, the discrepancy with the solar time relatively small, it is only a day for 133 years. More significant difference this calendar system with the phases of the Moon: 99 rpm it occurs within 29,530588 x 99 = 2923.53 days. Displacement of the phases of the moon of the calendar is about 1.53 days for eight years. Ekkadekaeterida – (calculated in vi. bc, the ancient Greek astronomer Kleostatom of Tenedos) 16-year cycle, synthesis oktaeteridy. Period consists of 105 full months and 93 months empty, which provides fairly good agreement between the lunar-solar calendar with the lunar phases and the duration synodic month: 105 x 30 + 93 x 29 = 5847: 29,53059 x 198 = 5847.0568.