It is also stated that Hera kidnapped Eileithyia, the goddess of childbirth, to prevent Leto from going into labor. The other gods tricked Hera into letting her go by offering her a necklace, nine yards (8 m) long, of amber. Mythographers agree that Artemis was born first and then assisted with the birth of Apollo, or that Artemis was born one day before Apollo, on the island of Ortygia and that she helped Leto cross the sea to Delos the next day to give birth to Apollo. Apollo was born on the seventh day (ἑβδομαγενής, hebdomagenes) of the month Thargelion —according to Delian tradition—or of the month Bysios—according to Delphian tradition. The seventh and twentieth, the days of the new and full moon, were ever afterwards held sacred to him.