Complex sentence: The Beta Israel calendar is an lunar calendar of 12 months, each has 29 or 30 days alternately, every four years there has been a leap year which added a full month (30 days).
Split into simpler sentences: The Beta Israel calendar is a lunar calendar of 12 months, each 29 or 30 days alternately. Every four years there has been a leap year which added a full month (30 days).