Class Times
- Modified Julian Date (MJD)
A continuous measure in days since midnight at the start of 17 November 1858. Based on UTC.
- Julian Day (JD)
MJD plus a fixed offset of 2400000.5. The number of days since the notional creation of the universe, midday on 1 Jan 4713 BC.
- ISO 8601
A string representation of the form
yyyy-mm-ddThh:mm:ss.s
, where theT
is a literal character (a space character may be used instead). Based on UTC.- Julian Epoch
A continuous measure based on a Julian year of exactly 365.25 days. For approximate purposes this resembles the fractional number of years AD represented by the date. Sometimes (but not here) represented by prefixing a 'J'; J2000.0 is defined as 2000 January 1.5 in the TT timescale.
- Besselian Epoch
A continuous measure based on a tropical year of about 365.2422 days. For approximate purposes this resembles the fractional number of years AD represented by the date. Sometimes (but not here) represented by prefixing a 'B'.
- Decimal Year
Fractional number of years AD represented by the date. 2000.0, or equivalently 1999.99recurring, is midnight at the start of the first of January 2000. Because of leap years, the size of a unit depends on what year it is in.
Therefore midday on the 25th of October 2004 is
2004-10-25T12:00:00
in ISO 8601 format,
53303.5 as an MJD value,
2004.81588 as a Julian Epoch and
2004.81726 as a Besselian Epoch.
Currently this implementation cannot be relied upon to better than a millisecond.
- Since:
- 2 Jun 2005
- Author:
- Mark Taylor (Starlink)
- See Also:
-
Field Summary
FieldsModifier and TypeFieldDescriptionstatic final double
JD value for MJD = 0 (=2400000.5). -
Method Summary
Modifier and TypeMethodDescriptionstatic double
besselianToMjd
(double besselianEpoch) Converts Besselian Epoch to Modified Julian Date.static double
dateToMjd
(int year, int month, int day) Converts a calendar date to Modified Julian Date.static double
dateToMjd
(int year, int month, int day, int hour, int min, double sec) Converts a calendar date and time to Modified Julian Date.static double
decYearToMjd
(double decYear) Converts a Decimal Year to a Modified Julian Date.static double
decYearToUnixSec
(double decYear) Converts a Decimal Year to seconds since 1970-01-01.static String
Converts a Modified Julian Date value to a date using a customisable date format.static double
Converts an ISO8601 date string to Modified Julian Date.static double
isoToUnixSec
(String isoDate) Converts an ISO8601 date string to seconds since 1970-01-01.static double
jdToMjd
(double jd) Converts a Julian Day to Modified Julian Date.static double
jdToUnixSec
(double jd) Converts a Julian day to seconds since 1970-01-01.static double
julianToMjd
(double julianEpoch) Converts a Julian Epoch to Modified Julian Date.static double
mjdToBesselian
(double mjd) Converts Modified Julian Date to Besselian Epoch.static String
mjdToDate
(double mjd) Converts a Modified Julian Date value to an ISO 8601-format date string.static double
mjdToDecYear
(double mjd) Converts a Modified Julian Date to Decimal Year.static String
mjdToIso
(double mjd) Converts a Modified Julian Date value to an ISO 8601-format date-time string.static double
mjdToJd
(double mjd) Converts a Modified Julian Date to Julian Day.static double
mjdToJulian
(double mjd) Converts a Modified Julian Date to Julian Epoch.static String
mjdToTime
(double mjd) Converts a Modified Julian Date value to an ISO 8601-format time-only string.static long
mjdToUnixMillis
(double mjd) Converts from modified Julian date to milliseconds since the Unix epoch (1970-01-01T00:00:00).static double
mjdToUnixSec
(double mjd) Converts a Modified Julian Date to seconds since 1970-01-01.static double
unixMillisToMjd
(long unixMillis) Converts from milliseconds since the Unix epoch (1970-01-01T00:00:00) to a modified Julian date value
-
Field Details
-
MJD_OFFSET
public static final double MJD_OFFSETJD value for MJD = 0 (=2400000.5).- See Also:
-
-
Method Details
-
isoToMjd
Converts an ISO8601 date string to Modified Julian Date. The basic format of theisoDate
argument isyyyy-mm-ddThh:mm:ss.s
, though some deviations from this form are permitted:- The '
T
' which separates date from time can be replaced by a space - The seconds, minutes and/or hours can be omitted
- The decimal part of the seconds can be any length, and is optional
- A '
Z
' (which indicates UTC) may be appended to the time
1994-12-21T14:18:23.2
", "1968-01-14
", and "2112-05-25 16:45Z
".- Parameters:
isoDate
- date in ISO 8601 format- Returns:
- modified Julian date corresponding to
isoDate
- Examples:
isoToMjd("2004-10-25T18:00:00") = 53303.75
,isoToMjd("1970-01-01") = 40587.0
- The '
-
dateToMjd
public static double dateToMjd(int year, int month, int day, int hour, int min, double sec) Converts a calendar date and time to Modified Julian Date.- Parameters:
year
- year ADmonth
- index of month; January is 1, December is 12day
- day of month (the first day is 1)hour
- hour (0-23)min
- minute (0-59)sec
- second (0<=sec<60)- Returns:
- modified Julian date corresponding to arguments
- Examples:
dateToMjd(1999, 12, 31, 23, 59, 59.) = 51543.99998
-
dateToMjd
public static double dateToMjd(int year, int month, int day) Converts a calendar date to Modified Julian Date.- Parameters:
year
- year ADmonth
- index of month; January is 1, December is 12day
- day of month (the first day is 1)- Returns:
- modified Julian date corresponding to 00:00:00 of the date specified by the arguments
- Examples:
dateToMjd(1999, 12, 31) = 51543.0
-
decYearToMjd
public static double decYearToMjd(double decYear) Converts a Decimal Year to a Modified Julian Date.- Parameters:
decYear
- decimal year- Returns:
- modified Julian Date
- Examples:
decYearToMjd(2000.0) = 51544.0
-
isoToUnixSec
Converts an ISO8601 date string to seconds since 1970-01-01. The basic format of theisoDate
argument isyyyy-mm-ddThh:mm:ss.s
, though some deviations from this form are permitted:- The '
T
' which separates date from time can be replaced by a space - The seconds, minutes and/or hours can be omitted
- The decimal part of the seconds can be any length, and is optional
- A '
Z
' (which indicates UTC) may be appended to the time
1994-12-21T14:18:23.2
", "1968-01-14
", and "2112-05-25 16:45Z
".- Parameters:
isoDate
- date in ISO 8601 format- Returns:
- seconds since the Unix epoch
- Examples:
isoToUnixSec("2004-10-25T18:00:00") = 1098727200
,isoToMjd("1970-01-01") = 0
- The '
-
decYearToUnixSec
public static double decYearToUnixSec(double decYear) Converts a Decimal Year to seconds since 1970-01-01.- Parameters:
decYear
- decimal year- Returns:
- seconds since the Unix epoch
- Examples:
decYearToUnixSec(2000.0) = 946684800
,decYearToUnixSec(1970) = 0
-
mjdToUnixSec
public static double mjdToUnixSec(double mjd) Converts a Modified Julian Date to seconds since 1970-01-01.- Parameters:
mjd
- modified Julian date- Returns:
- seconds since the Unix epoch
-
jdToUnixSec
public static double jdToUnixSec(double jd) Converts a Julian day to seconds since 1970-01-01.- Parameters:
jd
- Julian day- Returns:
- seconds since the Unix epoch
-
mjdToIso
Converts a Modified Julian Date value to an ISO 8601-format date-time string. The output format isyyyy-mm-ddThh:mm:ss
. If the result predates the Common Era, the string "(BCE)" is prepended.- Parameters:
mjd
- modified Julian date- Returns:
- ISO 8601 format date corresponding to
mjd
- Examples:
mjdToIso(53551.72917) = "2005-06-30T17:30:00"
-
mjdToDate
Converts a Modified Julian Date value to an ISO 8601-format date string. The output format isyyyy-mm-dd
. If the result predates the Common Era, the string "(BCE)" is prepended.- Parameters:
mjd
- modified Julian date- Returns:
- ISO 8601 format date corresponding to
mjd
- Examples:
mjdToDate(53551.72917) = "2005-06-30"
-
mjdToTime
Converts a Modified Julian Date value to an ISO 8601-format time-only string. The output format ishh:mm:ss
.- Parameters:
mjd
- modified Julian date- Returns:
- ISO 8601 format time corresponding to
mjd
- Examples:
mjdToTime(53551.72917) = "17:30:00"
-
mjdToDecYear
public static double mjdToDecYear(double mjd) Converts a Modified Julian Date to Decimal Year.- Parameters:
mjd
- modified Julian Date- Returns:
- decimal year
- Examples:
mjdToDecYear(0.0) = 1858.87671
-
formatMjd
Converts a Modified Julian Date value to a date using a customisable date format. The format is as defined by thejava.text.SimpleDateFormat
class. The default output corresponds to the string "yyyy-MM-dd'T'HH:mm:ss
"Note that the output from certain formatting characters (such as
MMM
for month,EEE
for day of week) is dependent on your locale (system language settings). The output time zone however always corresponds to UTC.- Parameters:
mjd
- modified Julian dateformat
- formatting patttern- Returns:
- custom formatted time corresponding to
mjd
- See Also:
- Examples:
formatMjd(50000.3, "EEE dd, MMM, yy") = "Tue 10 Oct, 95"
,formatMjd(50000.1234, "'time 'H:mm:ss.SSS") = "time 2:57:41.760"
-
jdToMjd
public static double jdToMjd(double jd) Converts a Julian Day to Modified Julian Date. The calculation is simplyjd-2400000.5
.- Parameters:
jd
- Julian day number- Returns:
- MJD value
-
mjdToJd
public static double mjdToJd(double mjd) Converts a Modified Julian Date to Julian Day. The calculation is simplyjd+2400000.5
.- Parameters:
mjd
- MJD value- Returns:
- Julian day number
-
mjdToJulian
public static double mjdToJulian(double mjd) Converts a Modified Julian Date to Julian Epoch. For approximate purposes, the result of this routine consists of an integral part which gives the year AD and a fractional part which represents the distance through that year, so that for instance 2000.5 is approximately 1 July 2000.- Parameters:
mjd
- modified Julian date- Returns:
- Julian epoch
- Examples:
mjdToJulian(0.0) = 1858.87885
-
julianToMjd
public static double julianToMjd(double julianEpoch) Converts a Julian Epoch to Modified Julian Date. For approximate purposes, the argument of this routine consists of an integral part which gives the year AD and a fractional part which represents the distance through that year, so that for instance 2000.5 is approximately 1 July 2000.- Parameters:
julianEpoch
- Julian epoch- Returns:
- modified Julian date
- Examples:
julianToMjd(2000.0) = 51544.5
-
mjdToBesselian
public static double mjdToBesselian(double mjd) Converts Modified Julian Date to Besselian Epoch. For approximate purposes, the result of this routine consists of an integral part which gives the year AD and a fractional part which represents the distance through that year, so that for instance 1950.5 is approximately 1 July 1950.- Parameters:
mjd
- modified Julian date- Returns:
- Besselian epoch
- Examples:
mjdToBesselian(0.0) = 1858.87711
-
besselianToMjd
public static double besselianToMjd(double besselianEpoch) Converts Besselian Epoch to Modified Julian Date. For approximate purposes, the argument of this routine consists of an integral part which gives the year AD and a fractional part which represents the distance through that year, so that for instance 1950.5 is approximately 1 July 1950.- Parameters:
besselianEpoch
- Besselian epoch- Returns:
- modified Julian date
- Examples:
besselianToMjd(1950.0) = 33281.92346
-
unixMillisToMjd
public static double unixMillisToMjd(long unixMillis) Converts from milliseconds since the Unix epoch (1970-01-01T00:00:00) to a modified Julian date value- Parameters:
unixMillis
- milliseconds since the Unix epoch- Returns:
- modified Julian date
-
mjdToUnixMillis
public static long mjdToUnixMillis(double mjd) Converts from modified Julian date to milliseconds since the Unix epoch (1970-01-01T00:00:00).- Parameters:
mjd
- modified Julian date- Returns:
- milliseconds since the Unix epoch
-