Just spotted , a lot of dates for posts are for three hundred years in the future ie 3/6/2323 , have I done a Rip Van Winkle?

It's probably because the date formats have been reset in your settings. There's an option for date format which is normally something like 'dd-mm-yy'. However it may be that your date format is something like dd/mm/yyyy, which would actually give a year of 2323 rather than 2023 like you would expect.