Calendar indicators have appeared on clocks since the late 17th century, but the first calendar clock patent was granted to John Hawes in 1853. Typically a separate face on these clocks showed the month, day of month, day of week, and often also lunar charts. Years later, the Ithaca Calendar Clock Company patented a mechanism to accurately account for leap years, resulting in what became known as the perpetual clock. Ithaca closed its doors in 1920.