Midsummer / Midwinter / are annual events. The Celts - in Western Europe - who incidently built boats and sailed around trading etc., had a very good calendar. Search for Celt on the net - I am too lazy to be finding the sites fer ya. The Irish-Scots who in these times were one Tribe, used the same system of reckoning. Note they actualy came out of southern Europe so THEY WERE NOT always in Pritani or Britain as it later came to be called. Hope that helps. :0)