Lunar-solar calendars are timekeeping systems that combine elements of both lunar and solar cycles. The lunar cycle is based on the phases of the moon, taking about 29.5 days to complete, while the solar cycle is based on the Earth's orbit around the sun, lasting about 365.25 days. This combination helps to align months with the seasons, ensuring that festivals and agricultural activities occur at appropriate times throughout the year. One well-known example of a lunar-solar calendar is the Hebrew calendar, which consists of 12 lunar months, with an additional month added periodically to keep it in sync with the solar year. Another example is the Chinese calendar, which also incorporates lunar months and adjusts for the solar year, influencing traditional festivals like Chinese New Year.