Placidus system is a time-proportional house system based on celestial motion. System gained popularity in late Renaissance, origin remains unclear. Magini first calculated mathematical foundations for current system. Placidus gave system new philosophical foundation and published house tables
Most US states observe DST, except Arizona, Hawaii, and US territories. DST starts March 2nd and ends November 1st, 2024. Clocks advance one hour in spring, revert one hour in fall. About 65% of US year is spent on DST
Japan Standard Time is 9 hours ahead of UTC (UTC+09:00). Before Meiji era, each region had its own time zone. 1886 Ordinance established 135° east longitude as standard meridian. Akashi became known as "Town of Time" at 135° longitude
Daytime occurs when Sun appears above local horizon. Approximately half of Earth is illuminated at any time. Sundial can record sun movement during daylight
Solar time is based on Sun's position in sky and synodic rotation period. Local apparent noon occurs when shadow points exactly north or south. Apparent solar time varies by up to 16 minutes due to Earth's orbit
Noon is 12 o'clock in the daytime, written as 12 noon or 12:00. The word "noon" originates from Latin nona hora, referring to Christian liturgical hours. The time gradually shifted from 12:00 to 12 noon in the 12th-14th centuries