On August 15, which is the official celebration of the Assumption of Mary, the village is far too crowded with too many tourists arriving to see all the girls in their traditional costumes. There is a dance at night, but this is also far too crowded.
Therefore, the locals want to have a more private celebration, which they do the day after. Make sure that if you want to see that, you try to be a little bit discreet, whatever that means. I think the best way is to have been there a few times before so people have got to know you and your presence around makes sense.
Olympians might be very hospitable and friendly, but during their celebrations they are not so happy to have other people dancing with them. They are free to watch of course. At first this didn't make much sense to me either, but after some time I spent with them, I got to kind feel the reasoning behind that.
You see the thing is that their celebrations are somewhat different from other places and have to do both with melancholy and sadness as well as happiness. There are times during their feast that you may see people crying or mourning because someone sang something about good old times or about a passed away relative.
In addition to the above, friends and family don't get many chances to see one another, because many of those people may live in the US, Piraeus or Rhodes. So they want to enjoy their time together. Having some outsider dancing with them in the wrong rhythm may just spoil the fun of it.
Finally, people there keep up to old traditions. Men can dance next to their sisters, other female relatives and their fiancés or wives. If they have a girlfriend, they are not allowed to be dancing next to her. Each one takes turns and moves to the front of the dance with his female co-dancers. So you understand, anyone who is an outsider would really look odd to this whole thing.
Don't get me wrong in that. This is not only for people coming from other countries. I am equally an outsider with any tourist there.
The party takes place in the central square (Selai) if the weather allows for it. The host is usually the Parthenon cafe, who is responsible to get food and beverages and apart from everything usual, a lot of whisky is available, as in all Olympian feasts. You will also see women offering treats out of big baskets that have monkey nuts, caramels and more.
You will see many women in their traditional costumes as well as girls in the traditional dresses, with many gold coins hanging from their necks.
The dancing keeps up until the morning, which is common to all Olympian feasts. The progression of it is really slow. The feast begins with table songs, then moves to Mantinades (on the spot improvised songs). In the mid-way of Mantinades, the dance begins in a really slow pace and builds up to a frenzy dance that goes up till the morning.