See the preamble to the latest Commentary update (4/9/02), 67 FR 16981, middle column, first paragraph, discussing the change in the comments regarding the definition of "business day":
"The comment is being adopted as
proposed. The comment does not
represent a new rule, but merely restates
and clarifies the requirement contained
in section 226.2(a)(6) of the regulation.
Consumers? ability to exercise their right
to rescind is not affected because
consumers can mail a notice of
rescission on the observed holiday; the
notice is not required to be postmarked
or delivered on that day. Consumers are
not likely to be confused because the
rescission notice must indicate the
specific date that the rescission period
expires. See § 226.15(b)(5),
§ 226.23(b)(1)(v).
A creditor may extend
the rescission period at its option." (emphasis added)
The publication is at
http://frwebgate.access.gpo.gov/cgi-bin/getdoc.cgi?dbname=2002_register&docid=02-8373-filed.pdf