JD
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Contents: Description, Arguments, Usage, Examples, Sub-Functions, Related Functions, Source Supported Under Version: > 1.14
Description Converts input date and time to UTC Julian Date
Arguments and Return Values Parameters: Numeric arrays specifying the year, month, day, hour, minute, second, time zone offset, and calendar mode. The calendar mode must be passed by reference, with the name cal. Return Value: A double-format numeric array with the same organization as the inputs
Usage Syntax: JD(year, month, day, hour, minute, second, time zone offset, cal=n) or JD(clock(1), cal=n) The Julian Date is a continuous count of days since noon UTC on January 1, 4713 BCE in the proleptic Julian calendar. The inputs specifying year, month, day, hour, minute, second, and time zone offset must be in that order. They can be scalar, or they can be (multi-element) arrays. Scalars and arrays can be mixed, but any arrays used must have the same dimensions. Time zone offset is (local time in hours) - (UTC time in hours). Most time zone offsets are integers. Eastern Standard Time is -5, and Mountain Standard Time is -7. The time zone offset is assumed to be zero (UTC) if not specified. The only required input is the year. Any omitted parts of the date are set to one, and the time, if omitted, defaults to noon (UTC). Thus JD(2009) returns the Julian Date of noon UTC on January 1, 2009. If the hour is given but minutes and seconds are omitted, minutes and seconds default to zero. If the hour and minute are given but seconds are omitted, seconds default to zero. For years before 1, use astronomical numbering, e.g. 4713 BCE = -4712. (There was no year 0.) This function also accepts date and time arrays in the format returned by the clock function. To quickly get the current Julian Date, enter JD(clock(1)). If the calendar mode is specified, it must be passed by reference, with the name cal and a value of 0 or 1. All other inputs should be passed by value. (See the examples.) If the calender mode is omitted, the function will guess, based on the latest input date. For (latest) input dates between October 15, 1582 and December 31, 1919 (when both calendar systems were in use), the function will print a warning about guessing the calendar mode. (Latest) dates before October 15, 1582 use the Julian calendar. (Latest) dates after that use the Gregorian (modern) calendar. This reflects the first changeover date. However, different countries changed at different times. See http://www.tondering.dk/claus/cal/node3.html The function cannot switch modes midway - it will compute using one calendar system OR the other for ALL members of an input array. If you want to find some JD's for some dates in the Julian calendar and some in the Gregorian calendar, you must enter them separately (that is, first enter the dates from the Julian calendar, then enter the dates from the Gregorian calendar, specifying modes). The formulae used here are from http://en.wikipedia.org/wiki/Julian_day and have been checked extensively against USNO calculator at http://aa.usno.navy.mil/data/docs/JulianDate.php The returned value is an integer if only the date (no time) is input. It is a double if any part of the time is input. When JD() is entered without any arguments, it prints its description, as shown below.
Examples dv> JD() Convert input date and time to UTC Julian Date JD(year, month, day, hour, minute, second, time zone offset, cal=n) or JD(clock(1), cal=n) returns the Julian Date (number of days since noon UTC on January 1, 4713 BC in the Julian calendar). The dates/times must be entered in the given order. For BCE, use astronomical year numbering, e.g. 4713 BCE = -4712 Works for array inputs cal (sets calendar mode) must be passed by reference cal=0 for Julian calendar; cal=1 for Gregorian (modern) calendar If cal is omitted, the function will guess, based on the date. (Latest) dates before October 15, 1582 use Julian calendar (Latest) dates after that use Gregorian calendar This reflects the first changeover date. However, different countries changed at different times. See http://www.tondering.dk/claus/cal/node3.html The function cannot switch modes midway - it will compute using one calendar system OR the other for ALL members of an input array. If you want to find some JD's for some dates in the Julian calendar and some in the Gregorian calendar, you must enter them separately (e.g. first enter the dates from Julian calendar, then enter the dates from the Gregorian calendar, specifying modes). Returns double-precision Julian Date if given date and time, integer Julian Day Number if only given date Formulae from http://en.wikipedia.org/wiki/Julian_day Checked extensively against USNO calculator at http://aa.usno.navy.mil/data/docs/JulianDate.php S.Marshall 04-10-2009 0 dv> JD(2009) 2454833 dv> JD(2009, 1) 2454833 dv> JD(2009, 1, 1) 2454833 dv> JD(2009, 1, 1, 12) 2454833.00000000 dv> JD(2009, 1, 1, 12, 0) 2454833.00000000 dv> JD(2009, 1, 1, 12, 0, 0) 2454833.00000000 dv> JD(2009, 1, 1, 12, 0, 0, -7) 2454833.29166667 dv> clock(1) 7x1x1 array of double, bsq format [56 bytes] 2009.00000000000 12.0000000000000 15.0000000000000 11.0000000000000 57.0000000000000 11.5374530000000 -7.0000000000000 dv> JD(clock(1)) 2455181.28976402 dv> a = create(12, start=1) 12x1x1 array of int, bsq format [48 bytes] 1 2 3 4 5 6 7 8 9 10 11 12 dv> JD(2009, a) 12x1x1 array of int, bsq format [48 bytes] 2454833 2454864 2454892 2454923 2454953 2454984 2455014 2455045 2455076 2455106 2455137 2455167 dv> JD(2009, a, 1) 12x1x1 array of int, bsq format [48 bytes] 2454833 2454864 2454892 2454923 2454953 2454984 2455014 2455045 2455076 2455106 2455137 2455167 dv> JD(2009, a, 15) 12x1x1 array of int, bsq format [48 bytes] 2454847 2454878 2454906 2454937 2454967 2454998 2455028 2455059 2455090 2455120 2455151 2455181 dv> JD(1918, 11, 11) Assuming Gregorian calendar 2421909 |
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Recent Library Changes Created On: 11-18-2009 |
