Class Times
- java.lang.Object
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- uk.ac.starlink.ttools.func.Times
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public class Times extends java.lang.Object
Functions for conversion of time values between various forms. The forms used are- Modified Julian Date (MJD)
A continuous measure in days since midnight at the start of 17 November 1858. Based on UTC.
- 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:
- ISO 8601 overview
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Method Summary
All Methods Static Methods Concrete Methods Modifier and Type Method Description static 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 java.lang.String
formatMjd(double mjd, java.lang.String format)
Converts a Modified Julian Date value to a date using a customisable date format.static double
isoToMjd(java.lang.String isoDate)
Converts an ISO8601 date string to Modified Julian Date.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 java.lang.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 java.lang.String
mjdToIso(double mjd)
Converts a Modified Julian Date value to an ISO 8601-format date-time string.static double
mjdToJulian(double mjd)
Converts a Modified Julian Date to Julian Epoch.static java.lang.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
unixMillisToMjd(long unixMillis)
Converts from milliseconds since the Unix epoch (1970-01-01T00:00:00) to a modified Julian date value
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Method Detail
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isoToMjd
public static double isoToMjd(java.lang.String isoDate)
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 '
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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
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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
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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
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mjdToIso
public static java.lang.String mjdToIso(double mjd)
Converts a Modified Julian Date value to an ISO 8601-format date-time string. The output format isyyyy-mm-ddThh:mm:ss
.- Parameters:
mjd
- modified Julian date- Returns:
- ISO 8601 format date corresponding to
mjd
- Examples:
mjdToIso(53551.72917) = "2005-06-30T17:30:00"
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mjdToDate
public static java.lang.String mjdToDate(double mjd)
Converts a Modified Julian Date value to an ISO 8601-format date string. The output format isyyyy-mm-dd
.- Parameters:
mjd
- modified Julian date- Returns:
- ISO 8601 format date corresponding to
mjd
- Examples:
mjdToDate(53551.72917) = "2005-06-30"
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mjdToTime
public static java.lang.String mjdToTime(double mjd)
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"
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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
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formatMjd
public static java.lang.String formatMjd(double mjd, java.lang.String format)
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:
SimpleDateFormat
- 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"
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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
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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
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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
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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
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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
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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
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