The festival was held at intervals of four years, at the time of the second or third full moon after the summer solstice, coming therefore in the late summer. During the lunar month in which it occurred a truce of the god was observed throughout Greece. For an armed force to set foot on the soil of the district of Elis within that period, or for anyone to do violence to travellers on their way to or from Olympia, was considered sacrilege. Heralds were sent to announce the coming celebration through all the states of Greece and to carry the news to the Greek colonies which had been established on the islands of the Ægean Sea, in southwestern Italy and Sicily, and along the shores of the Black Sea and the coast of Asia Minor, Syria, Egypt, Gaul, and Spain. From the whole of this wide area deputations and private citizens made their way to the sacred spot. It was essentially a Greek gathering, though many foreigners were doubtless present in the throng, and except the priestess of Demeter, who occupied a conspicuous seat in the stadium, no women were allowed to view the exercises. In the games which followed the sacrifices on the altar of Zeus none but free-born Greek citizens, of pure Hellenic descent and untainted by civil or religious crime, were allowed to have a share. Each contestant had passed through a long period of preliminary training, the last thirty days of which were spent in the gymnasia at Elis, thirty miles away to the northwest, or in later years the one at Olympia itself. Originally a single day had sufficed for the festival, but from time to time, as the occasion grew in importance, new features were added until finally the program required five days for its completion. Interest centered chiefly on the competitive exercises, which consumed the greater part of the time. The list of these varied in the course of years, with the addition or dropping out of one item or another, but in general they included the foot race—a single course (210 yards), or down and back, or back and forth a number of times, or a race in armor; the pentathlon; wrestling; boxing and the pancratium; races between men on horseback; and the chariot race, commonly with four horses, less frequently with two. As far back as the seventh century B.C. separate contests for boys in running, the pentathlon, wrestling, and boxing were introduced.