The California Court of Appeal faced a curious philosophical question in 1989: Do you become a year older on your birthday, or on the preceding day?

Paul Johnson had committed a robbery in San Francisco on Aug. 12, 1988, one day before his 18th birthday. The prosecution had charged him as an adult, arguing that “A person is in existence on the day of his birth. On the first anniversary he or she has lived one year and one day.”

Is that so? The appeals court didn’t buy it — Justice William Channell overruled the prior decisions and had Johnson tried as a juvenile.