The Sabine women are seized at the Consualia
Why Roman brides were carried over the threshold
Plutarch dates the seizure of the Sabine women by Romulus’ men to the eighteenth of Sextilis, the day of the Consualia games, and links Roman wedding customs to it.
Consualia dicta a Conso, quod tum feriae publicae ei deo et in Circo ad aram eius ab sacerdotibus ludi illi, quibus virgines Sabinae raptae.
The Consualia are named from Consus, because then there is a public holiday for that god, and at his altar in the Circus the priests hold those games at which the Sabine maidens were carried off.
Background
In Roman legend, Romulus' new city was full of men but short of women, and the neighbouring peoples refused to let their daughters marry them. Romulus announced games in honour of the god Consus, whose altar was in the valley of the Circus, and invited the Sabines and other neighbours to watch.
At a signal, the Roman men seized the young women among the spectators tradition. Plutarch says the cry they raised was "Talasius", and that this was why the word was still shouted at Roman weddings, though others explained it from talasia, spinning per Plutarch. He links other wedding customs to the story too: the bride did not step over her husband's threshold herself but was lifted over it, in memory of the Sabine women being carried in by force, and her hair was parted with the point of a spear.
Plutarch dates the seizure to the eighteenth of Sextilis, the day of the Consualia. Varro confirms that the Consualia were public games at Consus' altar in the Circus "at which the Sabine maidens were carried off" per Varro. For Romans, the founding story of marriage in their city began with violence, and was then said to end with reconciliation between the two peoples.
Before Caesar's reform (45 BC) the calendar had drifted from the seasons, so the real seasonal date was different; we don't give a modern equivalent. Why?