King Friday XIII, son of King Charming Thursday XII and Queen Cinderella Monday, is an avid arts lover, a talented whistler, and a former pole vaulter. He reigns over Calendarland with lots of pomp and poise, and he’s usually correct.

Fans of Mister Rogers’ Neighborhood may also remember that the monarch was born on Friday the 13th, because his birthday was celebrated on the program every Friday the 13th. Though the math isn’t perfect—according to Timeanddate.com, Friday the 13th sometimes happens two or three times a year—the heartwarming reason behind the unconventionally-timed birthday celebrations absolutely is.

Fred Rogers explained that he wanted to give children a reason to look forward to Friday the 13th, instead of buying into the negative superstitions that surround the dreaded date. “We thought, ‘Let’s start children out thinking that Friday the 13th was a fun day,’” he said in a 1999 interview. “So we would celebrate his birthday every time a Friday the 13th came.”

Rogers added that the tradition worked out so well partially because the show was broadcast live, and viewers knew to anticipate an especially festive episode whenever they spotted a Friday the 13th on the calendar.

Speaking of calendars: There’s an equally charming story behind the name Calendarland. In the same interview, Rogers disclosed that King Friday once asked children to write in with suggestions for his then-nameless country. One boy posited that since King Friday was named after a calendar date, his realm should be named after the calendar. Then, the lucky youngster was invited to the set, where King Friday christened him a prince of Calendarland.

King Friday might be king of Calendarland, but Mister Rogers is definitely the king of understanding how to make kids feel safe, smart, and special.