Editing Julian day (section)

== Terminology ==
The term ''Julian date'' may also refer, outside of astronomy, to the day-of-year number (more properly, the [[ordinal date]]) in the [[Gregorian calendar]], especially in computer programming, the military and the food industry,<ref name="usda">USDA {{Circa|1963}}.</ref> or it may refer to dates in the [[Julian calendar]]. For example, if a given "Julian date" is "October 5, 1582", this means that date in the Julian calendar (which was October 15, 1582, in the Gregorian calendar{{snd}}the date it was first established). Without an astronomical or historical context, a "Julian date" given as "36" most likely means the 36th&nbsp;day of a given Gregorian year, namely February 5. Other possible meanings of a "Julian date" of "36" include an astronomical Julian Day Number, or the year AD&nbsp;36 in the Julian calendar, or a duration of 36&nbsp;astronomical [[Julian year (astronomy)|Julian years]]). This is why the terms "ordinal date" or "day-of-year" are preferred. In contexts where a "Julian date" means simply an ordinal date, calendars of a Gregorian year with formatting for ordinal dates are often called ''"Julian calendars"'',<ref name="usda"/> but this could also mean that the calendars are of years in the Julian calendar system.

Historically, Julian dates were recorded relative to [[Greenwich Mean Time]] (GMT) (later, [[Ephemeris Time]]), but since 1997 the [[International Astronomical Union]] has recommended that Julian dates be specified in [[Terrestrial Time]].<ref>[https://www.iers.org/IERS/EN/Science/Recommendations/resolutionB1.html Resolution B1 on the use of Julian Dates] of the XXIIIrd International Astronomical Union General Assembly, Kyoto, Japan, 1997</ref> Seidelmann indicates that Julian dates may be used with [[International Atomic Time]] (TAI), [[Terrestrial Time]] (TT), [[Barycentric Coordinate Time]] (TCB), or [[Coordinated Universal Time]] (UTC) and that the scale should be indicated when the difference is significant.<ref>Seidelmann 2013, p. 15.</ref> The fraction of the day is found by converting the number of hours, minutes, and seconds after noon into the equivalent decimal fraction. Time intervals calculated from differences of Julian Dates specified in non-uniform time scales, such as UTC, may need to be corrected for changes in time scales (e.g. [[leap second]]s).<ref name="IAU" />