On July 14, the House of Representatives passed the Sunshine Protection Act by a vote of 308 to 117. The bill would impose Daylight Saving Time year-round, nationwide, and President Donald Trump has promised to sign it. It now sits in the Senate, where Majority Leader John Thune has voiced misgivings about a federal mandate, and Senator Tom Cotton has asked that it never reach the floor. The ensuing debate has been conducted entirely in terms of policy: circadian health versus evening commerce, school-bus-stop safety versus after-work golf. Those are pertinent questions, and they have a clear answer.

　　But there is an antecedent question that no one in Congress appears to have asked: where, exactly, does the federal government get the power to legislate noon away from the sun?

　　The question may sound quaint. But asking it exposes what the Sunshine Protection Act actually is—and reveals a limit on federal power that our constitutional tradition once understood clearly but has since forgotten. If the question sounds quaint, that’s itself collateral damage: the “substantial-effects” doctrine has told a century of legislators they needn’t ask which enumerated power a bill actually implements, since almost any activity can be conceived of, especially when considered in the aggregate, as affecting interstate commerce. I will return to that doctrine, because the answer to the present question about clock settings turns out to depend on it.

　　What Power Is Being Exercised?

　　Federal regulation of timekeeping rests on a statutory lineage that runs from the Standard Time Act of 1918—which the current bill amends directly—through the Uniform Time Act of 1966. That lineage is conventionally attributed to the commerce power, and its origin story explains why. The railroads, not Congress, created American time zones in 1883, to prevent trains, then running on dozens of incompatible local solar times, from colliding. The 1918 Act simply codified this coordination device. Scheduling, shipping, markets opening in sync, contracts bearing determinate meaning across state lines: if the Commerce Clause covers anything, this is it.

　　But notice what the coordination rationale supports: uniformity. Every benefit that makes federal time regulation a legitimate commerce measure is fully achieved at any uniform setting whatsoever. Trains don’t collide less often on Daylight Saving Time than on standard time. Markets synchronize identically on either. Coordination is achieved whether clocks are fixed to the sun or fixed an hour off from it.

　　This means the offset—the deliberate, permanent, nationwide misstatement of solar time by one hour—does zero commerce-facilitating work. Its entire function is to alter intrastate, largely non-commercial behavior: when many of us wake, when children walk to bus stops, when the after-work hours fall relative to sunset, when people golf and shop and dine. The offset is not a regulation of commerce among the several states. It is a behavioral-engineering project hijacking a coordination power, for the benefit of constituencies who have been refreshingly candid about their purpose. When the Senate Commerce Committee examined the question at its April 2025 hearing, the chairman’s own statement cited industry estimates that late-afternoon leagues account for up to 40 percent of some golf courses annual revenue, and that a single course would lose an estimated half-million dollars a year without the extra evening hour. The economic case for the offset, in other words, is not that it facilitates interstate commerce but that it transfers a valuable good—usable daylight—to particular industries, at the expense of everyone whose day begins before the late winter sunrise.

　　Chief Justice John Marshall anticipated this kind of maneuver. The same 1819 opinion that gave the federal government ample means to pursue its enumerated ends also set a limit: should Congress, under the pretext of executing its powers, pass laws for the accomplishment of objects not intrusted to the government, Marshall wrote in McCulloch v. Maryland, it would become the Court’s duty to invalidate them.

　　Modern doctrine has essentially retired pretext review. But the Sunshine Protection Act is a textbook example of Marshalls worry. The valid federal object—ensuring uniform time—is fully accomplished without the one-hour offset from mean solar noon. The offset serves a different object, one nowhere entrusted to Congress: deciding, for 330 million people, how the fixed endowment of daylight shall be distributed between morning and evening.

　　Fixing a Standard vs. Falsifying One

　　There is a second clause in play, and it’s conceptually the better fit. Defining standard time doesn’t look much like regulating a transaction; it looks like fixing a measure. And Article I, Section 8, Clause 5 of the US Constitution grants Congress the power to fix the Standard of Weights and Measures.

　　The power granted is to fix standards—to establish, stabilize, and render uniform accurate measures. The founding generation understood measurement standards as anchored, wherever possible, to invariable natural referents. Jeffersons 1790 report to Congress on weights and measures proposed deriving the basic unit of length from the seconds pendulum, precisely so the standard would rest on something in nature rather than on official whim. John Quincy Adamss 1821 Report on Weights and Measures—perhaps the most learned document ever produced by an American cabinet officer—treated the fidelity and uniformity of standards as the entire moral justification for the power, observing that weights and measures enter into the economical arrangements and daily concerns of every family.

　　To be clear, the two men located that anchor differently. Jefferson sought an invariable natural referent precisely so that the standard would not depend on anyone’s discretion. Adams, while admiring the French effort to find in matter or motion some immutable standard, concluded that no such referent was practically available, and recommended that “no innovation upon the existing weights and measures should be attempted”: the customary units had been refined by centuries of use, and their authority lay in settled practice rather than in nature. Jefferson feared official whim; Adams feared the disruption of every family’s existing dealings. Neither fear is assuaged by a standard Congress deliberately adjusts in order to transfer value from one group to another—redistribution masquerading as protection. The measurement power is a power of honest description. Government fixes the standard so private parties can rely on it; the standard serves its function only if it tells the truth.

　　Congress has the power to fix the standard of time, not the power to falsify it.

　　What would Clause 5 say about a Congress that redefined the foot as eleven inches to benefit sellers of lumber, or the pound as fourteen ounces to benefit grocers? No one would hesitate to call out these abuses of power. They’re not examples of fixing a standard; they are falsifying standards—using the governments monopoly over the conventions used to describe quantities to effect a transfer of the values being quantified. The seller who delivers eleven inches of lumber and calls it a foot has not been liberated from an inconvenient, antiquated convention. He has been handed, by statute, the value of one inch of his customers lumber.

　　The Sunshine Protection Act does precisely this with the meridian. Solar noon—the moment the sun crosses the local meridian—is the natural referent from which all civil timekeeping is derived. Standard time approximates it; zone time necessarily rounds local solar time to a common value within each band. But the rounding is an averaging toward the referent, exactly as a standardized foot replaced the various, incompatible local feet of medieval market towns. Time zones approximate, but only to the extent that accuracy must yield to coordination. The Daylight Saving offset, by contrast, is a deliberate, systematic, biased deviation away from the referent. It is adopted not to measure time more accurately or improve coordination, but to transfer an economic good from one group of residents to another.

　　The bills drafters have, perhaps inadvertently, confessed as much. The Act doesn’t merely extend Daylight Saving Time; it repeals the statutory provision that created it, then amends the Standard Time Act so that every zones standard time is redefined one hour forward—Eastern standard time, for instance, becomes four hours behind Greenwich rather than five. The deviation is not merely made permanent; it is made the standard, with nothing remaining in the statute books against which to measure the shift.

　　Some argue that all clock time is conventional, implying that it is also arbitrary. But selecting a convention between an honest approximation and an engineered distortion is exactly the choice Clause 5 addresses. The power to fix the standard is not a power to set it wherever the loudest and best-organized constituency prefers.

　　The bills exemption provision tells the whole story: states that had already opted out of DST—Arizona and Hawaii—may keep their sun-aligned clocks, but every other state is forbidden, forever, from choosing honest time. A statute that tolerates Arizonas deviation while foreclosing everyone elses is not pursuing uniformity; it is locking in a transfer.

　　What the Enacting Generations Understood

　　The first Congress to federally regulate time treated the two functions of coordination and offset as severable. The 1918 Act contained both the zone system and a wartime Daylight Saving provision, with the latter justified as an energy-conservation measure. When peace came, the political backlash was immediate, and in 1919 Congress repealed the DST provision over President Wilsons veto while leaving the zones untouched. Coordination survived; the offset did not. Even the generation that built the system understood that the constitutional core of federal time power was the honest uniform standard, and that deviation required an independent justification that no longer existed.

　　The political branches have since reached that judgment twice more. Year-round “War Time” ran from February 1942 until Congress repealed it within weeks of the war’s end. In 1974, under the oil embargo, the nation ran the experiment again; public support collapsed from 79 percent in December 1973 to 42 percent in February 1974, after barely a month of dark winter mornings. Congress restored standard time for the winter months before the next winter arrived. Three times, then, Congress itself has treated the offset as severable from the zones, and as unjustified the moment its wartime or energy rationale lapsed. As for the latter rationale, Senate Commerce Committee chairman Ted Cruz has acknowledged, at that same April 2025 hearing, that modern data show essentially no energy savings.

　　This narrow conception is consistent with the Supreme Court’s only construction of the federal time power. In Massachusetts State Grange v. Benton (1926), Justice Oliver Wendell Holmes found no conflict between the 1918 Act and Massachusettss own daylight saving law, construing the federal act to govern only federal affairs and matters within federal jurisdiction—leaving the states free to keep their clocks as they saw fit. The federal time power, as understood for its first half-century, coordinated the interstate sphere and stopped there. The Sunshine Protection Act inverts both halves of that understanding: it deploys federal time law precisely to restructure intrastate daily life, and it strips the states of the power to deviate that Grange assumed they possessed.

　　The federal time power is a composite—Clause 5 supplies the standard, Commerce the boundaries—and the Sunshine Protection Act rewrites the standard in service of commerce. Unfortunately, though, no federal court today is likely to strike down the Sunshine Protection Act. Under the substantial-effects doctrine, the offset gets “rational-basis” review, and Congresss assertion of economic benefits probably ends the inquiry. A century of acquiescence will do the rest. This would be just one more time a deferential standard of review has allowed Congress to do an end run around a specific, enumerated grant of power. Clause 5 empowers Congress to fix standards of weights and measures, not to falsify them. But once the substantial-effects doctrine supplies an alternative, essentially unbridled path to the same subject matter, the narrower grant’s limits become optional. Marshall’s since-abandoned pretext inquiry safeguarded against such a substitution.

　　But the Constitution isn’t addressed only to judges. Every senator now weighing this bill has sworn an oath to the Constitution, and the enumerated-powers inquiry is a discipline on legislation before it is a rule of decision for courts. That discipline asks a simple question here: which enumerated object does the DST offset serve? Not coordination—that is achieved without it. Not an honest standard—it’s deliberate deviation from one. The only candid answer is the one the golf industry testimony supplies: the offset serves the transferees’ purposes. Congress has the power to fix the standard of time, not the power to falsify it. The clock, like the ruler and the scale, should tell the truth. A government that will memory-hole the meridian for the benefit of its loudest and most organized petitioners should at least be required to name the power that permits it. A senator who can’t has a constitutional warrant—not merely a policy justification—for voting no.