I noticed a couple of spots in the code and manual with US daylight
savings rule as first sunday in April, which I believe is changing for
2007.

2006-12-20  Kevin Ryde  <user42@zip.com.au>

	* calendar/cal-dst.el (calendar-dst-starts): Default to second Sunday
	in March.
	(calendar-dst-ends): Default to first Sunday in November.
	These are new US rules commencing 2007, per tzdata
	ftp://elsie.nci.nih.gov/pub/.

and in the manual:

	* calendar.texi (Holidays): US daylight savings begins second Sunday
	in March for 2007 onwards.
	(Daylight Savings): Show new US default daylight savings rules, 2nd
	Sun in Mar to 1st Sun in Nov, now in cal-dst.el.

I'm not sure why daylight savings is mentioned in the "Holidays" node.
What it says about always using only the present definition isn't true
any more is it?  I'd be tempted to reduce the last paragraph to just
its first sentence.

	The dates used by Emacs for holidays are based on _current
	practice_, not historical fact.

Unless someone can think of a holiday where the rule has varied
historically.