A lunar year or lunar calendar is one that is based on the cycles of the moon phases. The problem with a lunar calendar is that it drifts away from the seasons. Each year, the start and end dates of each month drift by 11 days. To make the lunar calendar work in China, farmers would add in a leap month every 3 years.
Is lunar calendar accurate?
Lunar calendars may have been accurate when establishing months. But, its a bit off when it comes to the number of days there are in a year. A lunar year is only 354 days. So, if you were to use an accurate lunar calendar, you would lose 11 days annually compared to the widely used Gregorian Calendar.
Why do we not use a lunar calendar?
Lunar calendars are problematic, due partly to the fact that the average lunation is not a whole number. If 29 were the number used to mark the lunar month, the calendar would very quickly get out of sync with the actual phases of the moon. So what happens is that these calendars must be adjusted from time to time.