Every lunar month has four moon days. The most important are the New Moon (which begins the month) and the Full Moon (which is the middle of the month). On these days the sangha gathers to read the rules of monk behaviour and each monk examines himself to see if they have violated any of the rules. The other two moon days are halfway in between these two. Thus, there is therefore a moon day every seven days. Members of the laity often gather at the monastery on these days for religious activity.