As the Greeks changed from a poor country (one that mostly farmed for a living) to a richer country (one that also farmed, but became richer through warfare), the types of festivals began to change. To the ancient Greeks, a festival was like a giant party- one that the whole town was invited to.
But these festivals were not just all fun. The festivals of Ancient Greece had great religious importance. The festivals were put on whenever the Greeks' gods needed to be worshipped or the people were asking for a special favor from their god.
At these festivals there was usually one special god as the guest of honor. The festivals were also seasonal-meaning that they only happened at certain times of the year. However, these yearly cycles were not often correct because the Greeks kept track of their months differently than we do today. They did it in a different form of astronomy using the moon cycles instead of the sun cycles.
These months are called lunar months determined by one full moon to the next. This makes the months last about 29 and a half days, and because it's pretty hard to imagine a half day the Greek months alternated either 29 or 30 days. At the end of the Greek year, there were only 354 days, instead of our 356. As you can imagine, a couple of these years knocked the months off their seasons. Because of this, the festivals were set to occur on a specific date, not a season. To ensure that the months did not get too far off track, the Greeks allowed some of the months to occur twice in a year so that at the end of eight years, the cycle would start its months on the right season. At this point, the cycle would start all over again.
Each Greek month had the names of the festivals,
and each festival would fall into its corresponding month. The
existence of the gods and their activities were very real to the
average Greek, so the festivals were extremely important to show
the gods the people's thanks. These festivals were centers of
worship and thanksgiving, and the people showed such good will
that foreigners from other countries were also invited.