Mabon
Around 22 September
The second harvest, when the balance of light and dark is level and tipping toward the dark. Harvest-home customs across Britain cluster near it, including the corn dolly made from the last sheaf.
The name is a twentieth-century borrowing from Mabon ap Modron, a figure from the Mabinogion who has no traditional connection to the equinox at all.
As with Ostara, the observance is old and the label is new.