Margy Horowitz, a 37-year-old mother of two whom I know, is a private piano teacher in Los Angeles. She is an Orthodox Jew, as are about a third of her students. Paid per lesson, she forgoes up to $300 of income on each day she can't teach. And in the fall, when Rosh Hashanah ushers in a month-long series of multiday holidays, that adds up: seven missed workdays in just over three weeks, if no holidays fall on a weekend. "The income I lose," Horowitz said, "is an entire month's rent."
The second day of some Jewish holidays is mandated by rabbinic tradition, not Torah law. In today's world, they're increasingly hard to observe.