Charlotte Eisgrou and Ann Primack, the world's oldest known identical twins, turned 103, one week before they prepared to ring the bells to help usher in the new year.

Eisgrou and Primack, who live in South Florida and Daytona Beach, Fla., respectively, said that earning the title was a shock and that they both still enjoy good health.

"I didn't know that. That's wonderful," Primack told ABC by telephone, when she was told the news. "I can't believe it, that I've reached that age. The good thing is our minds are sharp. That's the only good thing."

Eisgrou told the Daytona Beach News-Journal "I feel wonderful. I have all my faculties." Neither she nor her twin sister use reading glasses or hearing aids.

Despite growing up inseparably, the twins did not always live close together during their adult lives. In 1949, Eisgrou moved to Florida with her second husband, leaving her sister behind in Chicago. The twins finally reunited for good in 1971, when Primack and her husband moved to Florida.

After the move, the twins said they visited each other often, taking long couples' vacations together. They have outlived their husbands and each woman had a son.

Eisgrou and Primack's record-holding longevity would have likely come as a surprise to anyone familiar with the twins' origins: the pair were born on Dec. 24, 1909, two months premature at a combined 7 pounds. Because incubators did not yet exist, their mother’s doctor wrapped them in blankets and kept them in the door of a stove on pillows, the twins said.

"He got the oven heated with a thermometer for as long as he wanted and he watched us and he took us out," Eisgrou said.

The improvisation appeared to have worked; both use a cane to walk, and say they are otherwise independent. Primack is an ovarian cancer survivor, they said.

As for health tips, the twins each have their own views. "It's the genes," Primack said in a 2009 interview. "Genes are the whole thing. And we were never fat."

"And it's milk," added Eisgrou. "We drank milk. It's milk and the genes."