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A continuous count of days used in astronomy.
Also known as: JD notation, Julian date astronomy
The Julian day number counts days continuously from a fixed origin in 4713 BC, without months, years or calendar reform. It exists so that intervals between astronomical events can be computed by subtraction, which calendar dates make surprisingly hard.
Counts days continuously from a fixed origin, without months or years, for astronomical timekeeping.
Contexts: Technical drawing, Maps
Allows an interval between two events to be found by subtraction, which is difficult with calendar dates spanning months, leap years or the Gregorian reform.
Contexts: Technical drawing, Maps
Begins its day at noon rather than at midnight, so that a night's observations fall within one Julian day.
Contexts: Technical drawing, Maps
A seven-digit numeral with a decimal fraction, printed in an observation record.