Hm, I googled for "daylight savings time" (with quotes) and I see ~299K hits. On the first page of hits, all but one of the titles were in the singular, and three of the blurbs include a corrective note: e.g., not Daylight Savings Time.

Also, since the USA thing is an official act of Congress, one could look up the official name of it. Saving. Each time they touched the act, on at least four different occasions, they named it in the singular.

Though I agree that English is a "living" language, Google ain't the definitive reference of proper spelling. If so, we should all say PERL, not Perl.