The Senate is unlikely to act before the end of the year on a House-passed bill that would make daylight saving time permanent, defying President Donald Trump and dashing the hopes of Americans who don’t like having to change their clocks twice a year.

As daylight saving time ends early Sunday and much of the country turns the clocks back an hour, several senators are holding up legislation that would eliminate the longtime U.S. practice. Supporters argue that ending the time change would provide more daylight during the afternoon, when Americans are most active, but opponents say commuters in some states wouldn’t see the sun until after 9 a.m.

“No one likes changing the clock, me included, but Congress has enacted permanent Daylight Savings Time multiple times before and repealed it each time once Americans experienced absurdly late sunrises in the winter,” said Sen. Tom Cotton, R-Ark.

Cotton, a member of GOP leadership, is the most vocal opponent of the change, notably drawing Trump’s ire earlier this month when the Republican president posted his personal cellphone number on social media and ordered him to “GET IT DONE!” But Cotton is not the only senator blocking the legislation, which would make daylight saving time the permanent national standard.

Several other Republicans, particularly those from some Northern states that would see much later sunrises, say they also oppose it.

“You’d be sending kids to school in the dark,” said South Dakota Sen. Mike Rounds.