Anecdote time: A few years ago I had too register for a ceremony in the university. They had few slots, and the date was a random day of the month announced in an obscure web page updated randomly. So the solution was to go every few days to look if the new one has been announced and try to register soon enough.
So I think tracking a date may be useful. It's more complicated because there are like a million of formats, dd/mm/yy, mm/dd/yy, MMMM dd, dd MMM, .... so it's not easy to support.
In my case, probably "something changed" was enough. But I guess in other case the announcement page my have a few independent parts that change for other reasons.
