TICTOC User's Guide




TICTOC is a `cookbook' example program that demonstrates use of the following two SPICELIB time conversion routines:

These routines convert between UTC and ET representations of time:

UTC

is a character string representation of Universal Time Coordinated, which may be in calendar, day of year, or Julian date format. UTC time strings are human-readable and thus suitable as user input.
ET

which stands for Ephemeris Time, is a double precision number of ephemeris seconds past Julian year 2000, also called Barycentric Dynamical Time. ET time is used internally in SPICELIB routines for reading ephemeris files.
When you run TICTOC, it will show you several examples of UTC time strings and their corresponding ET times. However, successful execution of the program is only the first step in learning about SPICELIB time conversion. Read the TICTOC source code to learn how to use SPICELIB routines to convert time in your own application programs. Also, refer to Time Required Reading and the UTC2ET and ET2UTC module headers for additional information.

To run TICTOC, you must know where a leapseconds kernel file is on your system. The following is a sample session which executes TICTOC.

( It is assumed that all of the necessary files are in the current directory. This particular session was run on a Sun using the UNIX operating system. ) 

 
   tictoc
 
 
                    Welcome to TICTOC
 
   This program demonstrates the use of the SPICELIB
   time conversion utility routines: UTC2ET and ET2UTC.
 
 
   Enter the name of a leapseconds kernel file:
   cookbook.tls
 
   Working ... Please wait.
 
 
         Example UTC time      :  9 JAN 1986 03:12:59.22451
 
         Corresponding ET      :   -441103565.591323
 
         UTC calendar format   :  1986 JAN 09 03:12:59.225
         UTC day of year format:  1986-009 // 03:12:59.225
         UTC Julian date format:  JD 2446439.634
 
   Continue? (Enter Y or N)
   Y
 
         Example UTC time      :  1/9/86 3:12:59.22451
 
         Corresponding ET      :   -441103565.591323
 
         UTC calendar format   :  1986 JAN 09 03:12:59.225
         UTC day of year format:  1986-009 // 03:12:59.225
         UTC Julian date format:  JD 2446439.634
 
   Continue? (Enter Y or N)
   Y
 
         Example UTC time      :  86-365//12:00
 
         Corresponding ET      :   -410313544.816091
 
         UTC calendar format   :  1986 DEC 31 12:00:00.000
         UTC day of year format:  1986-365 // 12:00:00.000
         UTC Julian date format:  JD 2446796.000
 
   Continue? (Enter Y or N)
   Y
 
         Example UTC time      :  JD 2451545
 
         Corresponding ET      :    57.1839272823855
 
         UTC calendar format   :  2000 JAN 01 12:00:00.000
         UTC day of year format:  2000-001 // 12:00:00.000
         UTC Julian date format:  JD 2451545.000
 
   Continue? (Enter Y or N)
   Y
 
         Example UTC time      :  77 JUL 1
 
         Corresponding ET      :   -710164751.815897
 
         UTC calendar format   :  1977 JUL 01 00:00:00.000
         UTC day of year format:  1977-182 // 00:00:00.000
         UTC Julian date format:  JD 2443325.500
 
   Continue? (Enter Y or N)
   Y
 
         Example UTC time      :  1 JUL '29
 
         Corresponding ET      :    930830457.184117
 
         UTC calendar format   :  2029 JUL 01 00:00:00.000
         UTC day of year format:  2029-182 // 00:00:00.000
         UTC Julian date format:  JD 2462318.500