"In light of global changes and the need, therefore, to reorient our national budget priorities, I have concluded that this project can be canceled without posing an unacceptable risk to the national security," the Democratic lawmaker said.
The master clocks - which use vibrating atoms to keep time within one- billionth of a second - are vital for synchronizing everything from warships' movements to bank transfers.
The Navy praised Byrd's decision. "We recognize and concur with the senator's efforts to ensure that tax dollars for defense are spent only on essential projects," said Cmdr. Stephen Pietropaoli, a Navy spokesman.
Byrd had earlier pushed aside Navy objections to building the clock in Green Bank, W.Va., where it would have created seven jobs.
"I do not ever recollect being told by the Navy that the clock was not wanted," Byrd wrote Navy officials last month after his clock quest began showing up in the press.
"The Navy has consistently told the senator that we don't need it," Gart Westerhout, the Naval Observatory's scientific director, said last month. But the Navy decided to build it "because the senator thought it would be a very good idea," he said.
But all is not lost for West Virginia.
Despite the loss of the clock, Byrd has ordered the Navy to spend $5 million to build a new radio telescope in Green Bank - at seven times the cost of leasing telescope time from a Massachusetts observatory.