Ah! The 'bug' I mention below is not a bug of course. It's just that each day's home page has a navigation calendar. As soon as a post is made to a new day the calendars on all the day home pages for that month need updated to add the new navigational URL. This is one of the downsides of static web pages.

The only way round this particular feature seems to be to incorporate a Javascript-driven calendar in an externa javascript file so tha the dynamic features of the page are separated from the static content.