Package uk.ac.starlink.ttools.func

Class Times

  • 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 the T 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

    • 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

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

    • Method Detail

      • isoToMjd

        public static double isoToMjd​(java.lang.String isoDate)
        Converts an ISO8601 date string to Modified Julian Date. The basic format of the isoDate argument is yyyy-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
        Some legal examples are therefore: "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

      • 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 AD
        month - index of month; January is 1, December is 12
        day - 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 AD
        month - index of month; January is 1, December is 12
        day - 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

      • 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 is yyyy-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"

      • 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 is yyyy-mm-dd.
        Parameters:
        mjd - modified Julian date
        Returns:
        ISO 8601 format date corresponding to mjd
        Examples:
        mjdToDate(53551.72917) = "2005-06-30"

      • 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 is hh: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

        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 the java.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 date
        format - 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"

      • 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