"They're over," a source tells the magazine. "It ended last month."
Both Swift, 21, and Gyllenhaal, 30, spent New Year's solo, with the country starlet at a party in Nashville and the Oscar-nominated actor in New York.
The two, who were first spotted together in October, spent Thanksgiving weekend together and were last seen together publicly in early December in Los Angeles.
Emails to Swift and Gyllenhaal's reps were not immediately returned.