Julianische

Julianische is the German adjective used to denote things related to Julius Caesar or to the Julian calendar. In historical and linguistic contexts, it often points to the calendar system introduced under Caesar or to the broader era named after him. The term also appears in astronomy and church contexts to distinguish from the later Gregorian system.

The Julian calendar was introduced in 45 BCE by Julius Caesar, with advice from the Alexandrian astronomer Sosigenes. It reformed the Roman calendar by adopting a solar year of 365 days and adding a leap day every four years. This produced a simple and regular cycle, but the calendar still overestimated the tropical year by a few minutes, causing a slow drift relative to the seasons.

By the 16th century the drift had accumulated to about 10 days, prompting the reform of the calendar. Pope Gregory XIII's calendar reform of 1582 realigned the date with the vernal equinox by skipping 10 days and modifying the leap year rule: century years are not leap years unless divisible by 400. The reform was adopted at different times across Europe and the world, leading to a staggered transition from the Julian to the Gregorian calendar.

Today, the Julian calendar survives in limited contexts. Some Eastern Orthodox churches continue to use the Julian calendar for liturgical dates, while others follow the Revised Julian calendar that aligns with the Gregorian most years. In civil life, Gregorian calendars are the global standard. In astronomy and chronology, the term Julian also appears in the concept of the Julian day, a continuous count of days used for precise time calculations.