Every Monday morning, Melinda French Gates has her calendar blocked to walk with her three closest female friends . “I’ve been incredibly lucky to have three female friends now for over 30 years,” French Gates tells Oprah Winfrey and Gayle King in an interview posted to her YouTube channel this week. “If you’re in town, you walk.

” In celebration of turning 60, French Gates , who recently announced a $1 billion donation to organizations and individuals at the forefront of gender equity , sat down with King and Winfrey for her series called “Moments That Make Us” to talk about the pearls of aging—and the power of female friendship. King and Winfrey have been friends for 50 years after meeting in Baltimore when 22-year-old Winfrey was the anchor and offered 21-year-old King a job as a production assistant. They tell French Gates that their lives would be wildly different if it weren’t for having each other’s ongoing support, which has taken them through job changes and King’s divorce.

“She fills a role for me that is as solid as mothering or sistering or anything could be,” Winfrey, age 70, says of King, age 69. Winfrey, at age 30, recalls being reluctant to take a new opportunity in Chicago. “Gayle was the only person who said, ‘I think you could do it,’” she says, praising King for believing in her potential.

“The reasons why I think our friendship has worked is because Gayle is happier—not happy but happier —for me for any kind of suc.