‘Mabon falls on the Autumn Equinox and is the second of the three harvest festivals (Lammas, Mabon, and Samhain). Just like Ostara on the opposite side of the Wheel of the Year, at Mabon the days and nights are of equal length. Though it’s typically celebrated on Sept 22 , the exact moment of the Equinox varies from year to year. This is due to a slight misalignment between the Gregorian calendar and the actual rate of the Earth’s rotation around the Sun. The Equinox also occurs at differing local times, so that depending on where you live, it may fall the day before or after the date listed on any given calendar. For this reason, a date range of September 21-24 is often cited in sources on the Wheel of the Year.
Though temperatures may still be warm during the day, summer has truly come to an end. The leaves on deciduous trees have begun to turn colors and fall to the ground, and there is a chill in the evening air. The days were longer than the nights until this moment, and after this the nights will begin their reign. The God is making his exit from the stage of the seasons, heading toward his symbolic death at Samhain in just a few short weeks. As with Ostara, the theme of balance is highlighted here, reminding us that everything is temporary, that no season lasts forever, and that neither dark nor light ever overpowers the other for long.
All Sabbats are occasions to express gratitude to the God and Goddess for the blessings in our lives, but Mabon is particularly so, coming at the height of the harvest season. Traditionally, this was a very busy and physically exhausting time. This holiday provided a brief rest from toiling in the fields—a day to sit back and enjoy the fruits of the labor thus far. In these modern times, most of us are not involved in agriculture, but we can still take a moment to rest from our labor and relax, appreciating all that we have. It is a time to recognize the need for balance between work and play.
But how should you celebrate Mabon? For starters, Mabon rituals can include decorating your altar with acorns, pine cones, seasonal fruits and nuts, and/or a few of the first colored leaves that drop from the trees. As with Lamas, harvest imagery like scythes and baskets can be used. Candles and altar cloths in autumn colors like rusty red, orange, brown, and gold are appropriate. If you have a feast, whether solo or with others, include seasonal vegetables like onions, potatoes, carrots and other root vegetables…’
— via Mabon (Autumn Equinox) – The Wiccan Calendar – Wicca Living