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Index Page tparse_c

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Procedure Abstract Required_Reading Keywords Brief_I/O Detailed_Input | Detailed_Output Parameters Exceptions Files Particulars Examples | Restrictions Literature_References Author_and_Institution Version Index_Entries

#### Procedure

       tparse_c ( Parse a UTC time string )

       void tparse_c ( ConstSpiceChar  * string,
                       SpiceInt          errmln,
                       SpiceDouble     * sp2000,
                       SpiceChar       * errmsg  )

#### Abstract

       Parse a time string and return seconds past the J2000 epoch
       on a formal calendar.

#### Required_Reading

       TIME

#### Keywords

       PARSING
       TIME

#### Brief_I/O

       VARIABLE  I/O  DESCRIPTION
       --------  ---  --------------------------------------------------
       string     I   Input time string, UTC.
       errmln     I   Available space in output error message string.
       sp2000     O   Equivalent UTC seconds past J2000.
       errmsg     O   Descriptive error message.

#### Detailed_Input

       string      is an input time string, containing a Calendar or Julian
                   Date. It may be in several different formats and can make
                   use of abbreviations. Several example strings and the
                   times that they translate to are listed below in the
                   -Examples section.

       errmln      is the maximum number of characters, including the
                   terminating null, that may be written to the output
                   error message string.

#### Detailed_Output

       sp2000      is the equivalent of UTC, expressed in UTC seconds past
                   J2000. If an error occurs, or if the input time string is
                   ambiguous, `sp2000' is not changed.

       errmsg      is a descriptive error message, which is empty when no
                   error occurs.

#### Parameters

       None.

#### Exceptions

       1)  If the `string' input string pointer is null, the error
           SPICE(NULLPOINTER) is signaled.

       2)  If the `string' input string has zero length, the error
           SPICE(EMPTYSTRING) is signaled.

       3)  If the `errmsg' output string pointer is null, the error
           SPICE(NULLPOINTER) is signaled.

       4)  If the `errmsg' output string has length less than two
           characters, the error SPICE(STRINGTOOSHORT) is signaled, since
           the output string is too short to contain one character of
           output data plus a null terminator.

#### Files

       None.

#### Particulars

       The input string is examined and the various components of a date
       are identified: julian date, year, month, day of year, day of
       month, hour, minutes, seconds. These items are assumed to be
       components on a calendar that contains no leapseconds (i.e. every
       day is assumed to have exactly 86400 seconds).

       tparse_c recognizes a wide range of standard time formats. The
       -Examples section contains a list of several common strings that
       are recognized and their interpretation. tparse_c relies on the
       lower level SPICELIB routine TPARTV to interpret the input string.

       Here is a brief summary of some of the basic rules used in the
       interpretation of strings.

       1)  Unless the substring "JD" or "jd" is present, the string is
           assumed to be a calendar format (day-month-year or year and
           day of year). If the substring JD or jd is present, the
           string is assumed to represent a Julian date.

       2)  If the Julian date specifier is not present, any integer
           greater than 999 is regarded as being a year specification.

       3)  A dash "-" can represent a minus sign only if it precedes
           the first digit in the string and the string contains
           the Julian date specifier (JD). (No negative years,
           months, days, etc. are allowed).

       4)  Numeric components of a time string must be separated
           by a character that is not a digit or decimal point.
           Only one decimal component is allowed. For example
           1994219.12819 is sometimes interpreted as the
           219th day of 1994 + 0.12819 days. tparse_c does not
           support such strings.

       5)  No exponential components are allowed. For example you
           can't specify the Julian date of J2000 as 2.451545E6.
           You also can't input 1993 Jun 23 23:00:01.202E-4 and have
           to explicitly list all zeros that follow the decimal
           point: i.e. 1993 Jun 23 23:00:00.0001202.

       6)  The single colon (:) when used to separate numeric
           components of a string is interpreted as separating
           Hours, Minutes, and Seconds of time.

       7)  If a double slash (//) or double colon (::) follows
           a pair of integers, those integers are assumed  to
           represent the year and day of year.

       8)  A quote followed by an integer less than 100 is regarded
           as an abbreviated year. For example: '93 would be regarded
           as the 93rd year of the reference century. See the SPICELIB
           routine TEXPYR for further discussion of abbreviated years.

       9)  An integer followed by "B.C." or "A.D." is regarded as
           a year in the era associated with that abbreviation.

       10) All dates are regarded as belonging to the extended
           Gregorian Calendar (the Gregorian calendar is the calendar
           currently used by western society). See the SPICELIB routine
           JUL2GR for converting from Julian Calendar to the Gregorian
           Calendar.

       11) If the ISO date-time separator (T) is present in the string
           ISO allowed token patterns are examined for a match
           with the current token list. If no match is found the
           search is abandoned and appropriate diagnostic messages
           are generated. Historically the interpretation of ISO
           formatted time strings deviates from the ISO standard in
           allowing two digit years and expanding years in the 0 to 99
           range the same way as is done for non ISO formatted strings.
           Due to this interpretation it is impossible to specify
           times in years in the 0 A.D. to 99 A.D. range using ISO
           formatted strings on the input.

       12) If two delimiters are found in succession in the time
           string, the time string is diagnosed as an erroneous string.
           (Delimiters are comma, white space, dash, slash, period, or
           day of year mark. The day of year mark is a pair of forward
           slashes or a pair of colons.)

           Note the delimiters do not have to be the same. The pair
           of characters ",-" counts as two successive delimiters.

       13) White space and commas serve only to delimit tokens in the
           input string. They do not affect the meaning of any
           of the tokens.

       14) If an integer is greater than 1000 (and the "JD" label
           is not present, the integer is regarded as a year.

       15) When the size of the integer components does not clearly
           specify a year the following patterns are assumed

           Calendar Format

              Year Month Day
              Month Day Year
              Year Day Month

              where Month is the name of a month, not its numeric
              value.

              When integer components are separated by slashes (/)
              as in 3/4/5. Month, Day, Year is assumed (2005 March 4)

           Day of Year Format.

              If a day of year marker is present (// or ::) the
              pattern

                I-I// or I-I:: (where I stands for an integer)

              is interpreted as Year Day-of-Year. However, I-I/ is
              regarded as ambiguous.

       To understand the complete list of strings that can be understood
       by tparse_c you need to examine the SPICELIB routine TPARTV and read
       the appendix to the TIME required reading entitled "Parsing Time
       Strings."

       tparse_c does not support the specification of time system
       such as TDT or TDB; AM/PM specifications of time; or time
       zones (such as PDT, UTC+7:20, etc.).

       If some part of the time string is not recognized or if
       the meaning of the components are not clear, an error string
       is constructed that explains the problem with the string.

       Since the routine works by breaking the input string into
       a sequence of tokens whose meanings are determined by position
       and magnitude, you can supply strings such as 1993 FEB 35 and
       have this correctly interpreted as March 7, 1993. However,
       this default action can be modified so that only "proper"
       calendar dates and times are recognized. To do this call
       the routine tparch_c as shown below:

          tparch_c ( "YES" );

       This will cause the routine to treat dates and times with
       components outside the normal range as errors.

       To return to the default behavior

          tparch_c ( "NO" );

       This routine returns information about parse errors in the output
       string `errmsg'.

#### Examples

       The numerical results shown for these examples may differ across
       platforms. The results depend on the SPICE kernels used as
       input, the compiler and supporting libraries, and the machine
       specific arithmetic implementation.

       1) Parse a series of time strings representing calendar dates and
          output number of seconds past J2000 epoch that corresponds to
          each of them. Some of the input strings have an invalid format
          which is reflected in their output.

          Example code begins here.

          /.
             Program tparse_ex1
          ./
          #include <stdio.h>
          #include "SpiceUsr.h"

          int main( )
          {
             /.
             Local constants
             ./
             #define ERRMLN          37

             /.
             Local variables.
             ./
             SpiceChar               errmsg [ ERRMLN ];
             SpiceDouble             sp2000;
             SpiceInt                i;

             /.
             Assign an array of calendar dates. Not all of them are
             valid.
             ./
             SpiceChar             * date[] =  { "1986-01-18T12:19:52.18",
                                                 "17JUN1982 18:28:28",
                                                 "182-'92/ 12:28:29.182",
                                                 "'67-271/ 12:28:30.291",
                                                 "-467-14-25 26:00:75",
                                                 "1993 FEB 35",
                                                 "1993 MAR 7"            };

             /.
             Loop over the `date' array, call tparse_c for each element.
             ./
             printf( "    Input string        UTC sec past J2000\n" );
             printf( "----------------------  ------------------\n" );

             for (i = 0; i < 7; i++ )
             {
                tparse_c ( date[i], ERRMLN, &sp2000, errmsg );

                if ( iswhsp_c(errmsg) )
                {
                   printf ( "%-22s  %18.6f\n", date[i], sp2000 );
                }
                else
                {
                   printf ( "%-22s  %s\n", date[i], errmsg );
                }
             }

             return ( 0 );
          }

          When this program was executed on a PC/Linux/gcc/64-bit
          platform, the output was:

              Input string        UTC sec past J2000
          ----------------------  ------------------
          1986-01-18T12:19:52.18   -440293207.820000
          17JUN1982 18:28:28       -553541492.000000
          182-'92/ 12:28:29.182    -236820690.818000
          '67-271/ 12:28:30.291    2137710510.291000
          -467-14-25 26:00:75     An unexpected delimiter ('-') was en
          1993 FEB 35              -215265600.000000
          1993 MAR 7               -215265600.000000

          Note that the "1993 FEB 35" string in converted to UTC seconds
          past J2000, interpreted as "1993 MAR 7". Also note that the
          error message resulting from parsing "-467-14-25 26:00:75"
          is truncated to the provided ERRMLN length.

       2) Below is a sampling of some of the time formats that are
          acceptable as inputs to tparse_c. A complete discussion of
          permissible formats is given in the reference document
          time.req.

          ISO (T) Formats.

          String                        Year Mon  DOY DOM  HR Min Sec
          ----------------------------  ---- ---  --- ---  -- --- -----
          1996-12-18T12:28:28           1996 Dec   na  18  12  28 28
          1986-01-18T12                 1986 Jan   na  18  12  00 00
          1986-01-18T12:19              1986 Jan   na  18  12  19 00
          1986-01-18T12:19:52.18        1986 Jan   na  18  12  19 52.18
          1986-01-18T12:19:52.18Z       1986 Jan   na  18  12  19 52.18
          1995-08T18:28:12              1995  na  008  na  18  28 12
          1995-08T18:28:12Z             1995  na  008  na  18  28 12
          1995-18T                      1995  na  018  na  00  00 00
          0000-01-01T                   1 BC Jan   na  01  00  00 00

          Calendar Formats.

          String                        Year   Mon DOM  HR Min  Sec
          ----------------------------  ----   --- ---  -- ---  ------
          Tue Aug  6 11:10:57  1996     1996   Aug  06  11  10  57
          1 DEC 1997 12:28:29.192       1997   Dec  01  12  28  29.192
          2/3/1996 17:18:12.002         1996   Feb  03  17  18  12.002
          Mar 2 12:18:17.287 1993       1993   Mar  02  12  18  17.287
          1992 11:18:28  3 Jul          1992   Jul  03  11  18  28
          June 12, 1989 01:21           1989   Jun  12  01  21  00
          1978/3/12 23:28:59.29         1978   Mar  12  23  28  59.29
          17JUN1982 18:28:28            1982   Jun  17  18  28  28
          13:28:28.128 1992 27 Jun      1992   Jun  27  13  28  28.128
          1972 27 jun 12:29             1972   Jun  27  12  29  00
          '93 Jan 23 12:29:47.289       1993*  Jan  23  12  29  47.289
          27 Jan 3, 19:12:28.182        2027*  Jan  03  19  12  28.182
          23 A.D. APR 4, 18:28:29.29    0023** Apr  04  18  28  29.29
          18 B.C. Jun 3, 12:29:28.291   -017** Jun  03  12  29  28.291
          29 Jun  30 12:29:29.298       2029+  Jun  30  12  29  29.298
          29 Jun '30 12:29:29.298       2030*  Jun  29  12  29  29.298

          Day of Year Formats.

          String                        Year  DOY HR Min Sec
          ----------------------------  ----  --- -- --- ------
          1997-162::12:18:28.827        1997  162 12  18 28.827
          162-1996/12:28:28.287         1996  162 12  28 28.287
          1993-321/12:28:28.287         1993  231 12  28 28.287
          1992 183// 12:18:19           1992  183 12  18 19
          17:28:01.287 1992-272//       1992  272 17  28 01.287
          17:28:01.282 272-1994//       1994  272 17  28 01.282
          '92-271/ 12:28:30.291         1992* 271 12  28 30.291
          92-182/ 18:28:28.281          1992* 182 18  28 28.281
          182-92/ 12:29:29.192          0182+ 092 12  29 29.192
          182-'92/ 12:28:29.182         1992  182 12  28 29.182

          Julian Date Strings.

          jd 28272.291                  Julian Date   28272.291
          2451515.2981 (JD)             Julian Date 2451515.2981
          2451515.2981 JD               Julian Date 2451515.2981

                                       Abbreviations Used in Tables

                                          na    --- Not Applicable
                                          Mon   --- Month
                                          DOY   --- Day of Year
                                          DOM   --- Day of Month
                                          Wkday --- Weekday
                                          Hr    --- Hour
                                          Min   --- Minutes
                                          Sec   --- Sec

          *  The default interpretation of a year that has been
             abbreviated to two digits with or without a leading quote
             as in 'xy or xy (such as '92 or 92) is to treat the year as
             19xy if xy > 68 and to treat it as 20xy otherwise. Thus '70
             is interpreted as 1970 and '67 is treated as 2067. However,
             you may change the "split point" and centuries through use
             of the CSPICE routine tsetyr_c. See that routine for a
             discussion of how you may reset the split point.

          ** All epochs are regarded as belonging to the Gregorian
             calendar. We formally extend the Gregorian calendar backward
             and forward in time for all epochs. If you have epochs
             belonging to the Julian Calendar, consult the SPICELIB
             routines TPARTV and JUL2GR for a discussion concerning
             conversions to the Gregorian calendar and ET. The routines
             timdef_c and str2et_c, used together, also support conversions
             from Julian Calendar epochs to ET.

          +  When a day of year format or calendar format string is
             input and neither of the integer components of the date is
             greater than 1000, the first integer is regarded as being
             the year.

          Any integer greater than 1000 is regarded as a year
          specification. Thus 1001-1821//12:28:28 is interpreted as
          specifying two years and will be rejected as ambiguous.

#### Restrictions

       None.

#### Literature_References

       None.

#### Author_and_Institution

       N.J. Bachman        (JPL)
       M. Costa Sitja      (JPL)
       J. Diaz del Rio     (ODC Space)
       J.M. Lynch          (JPL)
       W.M. Owen           (JPL)
       M.J. Spencer        (JPL)
       W.L. Taber          (JPL)
       I.M. Underwood      (JPL)

#### Version

       -CSPICE Version 1.1.0, 23-DEC-2021 (JDR) (MCS)

           Changed the input argument name "lenout" to "errmln" for
           consistency with other routines.

           Edited the header to comply with NAIF standard. Added complete
           code example.

           Updated the -Exceptions and -Particulars sections.

           Added TIME to -Required_Reading list.

       -CSPICE Version 1.0.1, 23-JUL-2015 (NJB)

           Filled in -Exceptions section of header.

       -CSPICE Version 1.0.0, 05-JUN-1999 (NJB) (JML) (WMO) (MJS) (IMU) (WLT)

#### Index_Entries

       parse a utc time string

#### Link to routine tparse_c source file tparse_c.c

    Fri Dec 31 18:41:14 2021