| timout_c |
|
Table of contents
Procedure
timout_c ( Time Output )
void timout_c ( SpiceDouble et,
ConstSpiceChar * pictur,
SpiceInt outlen,
SpiceChar * output )
AbstractConvert an input epoch represented in TDB seconds past the TDB epoch of J2000 to a character string formatted to the specifications of a user's format picture. Required_ReadingTIME KeywordsTIME Brief_I/OVARIABLE I/O DESCRIPTION -------- --- -------------------------------------------------- et I Epoch in seconds past the ephemeris epoch J2000. pictur I A format specification for the output string. outlen I Maximum length of output string `output'. output O A string representation of the input epoch. Detailed_Input
et is a double precision representation of time in seconds
past the ephemeris epoch J2000.
pictur is a string that specifies how the output should be
presented. The string is made up of various markers
that stand for various components associated with
a time.
There are five types of markers that may appear in a
format picture. These are String Markers, Numeric
Markers, Meta markers, Modifier Markers and Literal
Markers.
The `pictur' string is examined and the various markers
are identified. The output time string is constructed
by replacing each of the identified markers with
an appropriate time component.
The various markers and their meanings are discussed
in the -Particulars section below.
Note that leading and trailing blanks in `pictur' are
ignored.
outlen is the maximum allowed length of the output string
`output'. This length must be large enough to hold the
output string plus the null-terminator character. If the
output string is expected to have N characters, `outlen'
should be at least N+1.
Detailed_Output
output is a time string equivalent to the input epoch `et',
matching the format specified by `pictur'.
ParametersNone. Exceptions1) A leapseconds kernel must be loaded via the routine furnsh_c before calling this routine. If a leapsecond kernel has not been loaded, an error is signaled by a routine in the call tree of this routine. 2) If `pictur' contains the numeric marker "YYYY" and the magnitude of year is too large to be displayed as a four-digit integer, timout_c will replace it by "****". 3) If the requested precision is higher than 12 decimal places, timout_c will truncate the decimal part down to 12, and `output' will have all the remaining digits in the decimal part set to zero. 4) Double colon (::), when is not part of one of the supported markers, has no effect and will be presented as is on the output string. 5) If the `pictur' input string pointer is null, the error SPICE(NULLPOINTER) is signaled. 6) If the `pictur' input string has zero length, the error SPICE(EMPTYSTRING) is signaled. 7) If the `output' output string pointer is null, the error SPICE(NULLPOINTER) is signaled. 8) If the `output' 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. FilesA leapseconds kernel must be "loaded" via the routine furnsh_c prior to calling timout_c. Particulars
A format picture is simply a string of letters that lets
timout_c know where various components of a time representation
should be placed during creation of the time string.
Here's an example of such a picture:
MON DD,YYYY HR:MN:SC.#### (TDB) ::TDB
Here is a sample of times that would be created by using this
format.
JAN 12,1992 12:28:18.2772 (TDB)
FEB 13,1994 23:18:25.2882 (TDB)
AUG 21,1995 00:02:00.1881 (TDB)
As you can see from the samples above, the format picture
specifies that every time string created should begin with a
three-letter abbreviation for the month, followed by a space and
the day of the month. The day of month is followed immediately by
a comma and the year. The year component is followed by two
spaces. The next outputs are hours represented as a two digit
integer, a colon, minutes represented as a two digit integer,
another colon, and seconds truncated to 4 decimal places and
having a two digit integer part (rounding can be commanded; see
the discussion of truncation and rounding below). This is
followed by a space and the string "(TDB)". The special marker
"::TDB" in the time picture is a ``invisible'' marker. It is
used to specify the time system that should be used in creating
the time string (in this case Barycentric Dynamical Time).
timout_c does not recognize all of the parts of the time format
picture in the example above. The list of recognized parts and
unrecognized parts is shown in the table below.
Recognized Unrecognized
---------- ------------
"MON" " "
"DD" ","
"YYYY" " "
"HR" ":"
"MN" "(TDB)"
"SC"
".####"
"::TDB"
The unrecognized parts are called literal markers. They are
copied exactly as they appear in `pictur' into the output string.
The recognized parts of the picture are replaced by a
component of time or, as in the case of "::TDB" are used
as instructions about the overall properties of the time
string.
The full list of recognized markers, their classification
and meaning are given below.
MARKER CLASS MEANING
----------- -------- -----------------------------------------
".##..." modifier represents a numeric component that
immediately precedes this in a decimal
format. Number of decimal places
equals the number of '#' characters
"::GCAL" meta dates are reported in Gregorian calendar
"::JCAL" meta dates are reported in Julian calendar
"::MCAL" meta dates after 15 October, 1582 are reported
in Gregorian calendar; before that
dates are reported in Julian calendar
"::RND" meta round output to places specified by
least significant component
"::TDB" meta all components should be TDB
"::TDT" meta all components should be TT (TDT)
"::TT" meta all components should be TT (TDT)
"::TRNC" meta truncate all output components (default)
"::UTC" meta all components should be UTC (default)
"::UTC+h:m" meta all components in UTC offset by +h (hours)
and +m (minutes) so as to allow time zones.
"::UTC-h:m" meta all components in UTC offset by -h (hours)
and -m (minutes) so as to allow time zones.
"AMPM" string String (either "A.M." or "P.M.")
indicating whether hours are before
or after noon.
"ampm" string String (either "a.m." or "p.m.")
indicating whether hours are before
or after noon.
"AP" numeric AM/PM equivalents of the hour component
of a time.
"DD" numeric Day of month
"DOY" numeric Day of year
"ERA" string String (either "B.C." or "A.D.") giving
era associated with an epoch.
"?ERA?" string String: either " B.C. " or " A.D. " if the
year is before 1000 A.D. otherwise a
blank: " ".
"era" string String (either "b.c." or "a.d.") giving
era associated with an epoch.
"?era?" string String: either " b.c. " or " a.d. " if the
year is before 1000 A.D. otherwise a
blank: " ".
"HR" numeric hour component of time
"JULIAND" numeric Julian date component of time
"MM" numeric numeric representation of month component
"MN" numeric minute component of time
"MON" string upper case three letter abbreviation for
month
"Mon" string capitalized three letter abbreviation for
month
"mon" string lower case three letter abbreviation for
month
"MONTH" string upper case full name of month
"Month" string capitalized full name of month
"month" string lower case full name of month
"SC" numeric seconds component of time
"SP1950" numeric seconds past 1950 component of time
"SP2000" numeric seconds past 2000 component of time
"YR" numeric last two digits of year component of time
"YYYY" numeric year component of time
"WEEKDAY" string upper case day of week
"Weekday" string capitalized day of week
"weekday" string lower case day of week
"WKD" string upper case three letter abbreviation for
day of week.
"Wkd" string capitalized three letter abbreviation for
day of week.
"wkd" string lower case three letter abbreviation for
day of week.
String Markers
String markers are portions of the format picture that will
be replaced with a character string that represents the
corresponding component of a time.
Numeric Markers
Numeric markers are portions of the format picture that will
be replaced with a decimal string that represents the
corresponding component of a time.
Meta Markers
Meta markers (listed under the class ``meta'' in the
table above) are used to indicate "global" properties of
your time string. You may specify time scale and how
rounding should be performed on the components of time
in your output string. Meta markers may be placed anywhere
in your format picture. They do not contribute to placement
of characters in output time strings. Also there are no
restrictions on how many meta markers you may place in
the format picture. However, if you supply conflicting
`meta' markers (for example "::TDT" and "::TDB") in your
picture the first marker listed (in left to right order)
overrules the conflicting marker that appears later in
the picture.
Default Meta Markers
If you do not specify a time system, calendar, or time
zone through the use of a Meta Marker, timout_c uses the
values returned by the SPICE routine timdef_c. The default
time system, calendar returned by timdef_c are UTC and
the Gregorian calendar. The default time zone returned
by timdef_c is a blank indicating that no time zone offset
should be used.
See the header for the routine timdef_c for a more complete
discussion of setting and retrieving default values.
Modifier Markers
The numeric markers listed in the table above stand
for integers unless they are modified through use of a
modifier marker. The strings
.#
.##
.###
.####
are used to this end. When a numeric marker is followed
immediately by one of these modifiers, the corresponding time
component will be written with the number of decimal places
indicated by the number of successive occurrences of the
character '#'. Any numeric token may be modified.
Rounding vs. Truncation
The meta markers ::TRNC and ::RND allow you to control
how the output time picture is rounded. If you specify
::TRNC all components of time are simply truncated to
the precision specified by the marker and any modifier.
If you specify ::RND the output time is rounded to the
least significant component of the format picture. The
default action is truncation.
Whether an output time string should be rounded or
truncated depends upon what you plan to do with the
string. For example suppose you simply want to get the
calendar date associated with a time and not the time of
day. Then you probably do not want to round your output.
Rounding 1992 Dec 31, 13:12:00 to the nearest day
produces 1993 Jan 1. Thus in this case rounding is probably
not appropriate.
However, if you are producing output for plotting using
Julian Date, seconds past 1950 or seconds past 2000, you will
probably want your output rounded so as to produce a smoother
plot.
Time Systems
timout_c can produce output strings for epochs relative to
any of the systems UTC, TT or TDT, or TDB. If you do not
explicitly specify a time system, timout_c will produce strings
relative to the time system returned by the SPICE routine
timdef_c. Unless you call timdef_c and change it, the default time
system is UTC. However, by using one of the Meta Markers
::UTC, ::TT, ::TDT, or ::TDB you may specify that timout_c
produce time strings relative to the UTC, TT or TDT, or TDB
system respectively.
Time Zones
The meta markers ::UTC+h:m and ::UTC-h:m allow you to
offset UTC times so that you may represent times in a time
zone other than GMT. For example you can output times in
Pacific Standard time by placing the meta-marker ::UTC-8 in
your format picture.
For instance, if you use the picture
YYYY Mon DD, HR:MN:SC ::UTC
you will get output strings such as:
1995 Jan 03, 12:00:00
If you use the picture
YYYY Mon DD, HR:MN:SC ::UTC-8
you will get output strings such as:
1995 Jan 03, 04:00:00
Finally, if you use the picture
YYYY Mon DD, HR:MN:SC ::UTC-8:15
you will get output string
1995 Jan 03, 03:45:00
Note that the minutes are always added or subtracted based on
the sign present in the time zone specifier. In the case of
::UTC+h:m, minutes are added. In the case ::UTC-h:m, minutes
are subtracted.
The unsigned part of the hours component can be no more than
12. The unsigned part of the minutes component can be no
more than 59.
Calendars
The calendar currently used by western countries is the
Gregorian calendar. This calendar begins on Oct 15, 1582.
Prior to Gregorian calendar the Julian calendar was used. The
last Julian calendar date prior to the beginning of the
Gregorian calendar is Oct 5, 1582.
The primary difference between the Julian and Gregorian
calendars is in the determination of leap years. Nevertheless,
both can be formally extended backward and forward in time
indefinitely.
By default timout_c uses the default calendar returned by
timdef_c. Under most circumstances this will be the Gregorian
calendar (::GCAL). However you may specify that timout_c use a
specific calendar through use of one of the calendar Meta
Markers. You may specify that timout_c use the Julian calendar
(::JCAL), the Gregorian calendar (::GCAL) or a mixture of
both (::MCAL).
If you specify ::MCAL, epochs that occur after the beginning
of the Gregorian calendar will be represented using the
Gregorian calendar, and epochs prior to the beginning of the
Gregorian calendar will be represented using the Julian
calendar.
Getting Software to Construct Pictures for You.
Although it is not difficult to construct time format
pictures, you do need to be aware of the various markers that
may appear in a format picture.
There is an alternative means for getting a format picture.
The routine tpictr_c constructs format pictures from a sample
time string. For example, suppose you would like your time
strings to look like the basic pattern of the string below.
"Fri Jul 26 12:22:09 PDT 1996"
You can call tpictr_c with this string, and it will create the
appropriate `pictur' for use with timout_c.
tpictr_c ( "Fri Jul 26 12:22:09 PDT 1996", LENPIC, LENERR,
pictur, &ok, errmsg );
The result will be:
"Wkd Mon DD HR:MN:SC (PDT) ::UTC-7"
Note: not every date that you can read is interpretable by
tpictr_c. For example, you might be able to understand that
19960212121116 is Feb 2 1996, 12:11:16. However, tpictr_c
cannot recognize this string. Thus it is important to check
the logical output OK to make sure that tpictr_c was able to
understand the time picture you provided.
Even thought tpictr_c can not recognize every time pattern that
has been used by various people, it does recognize nearly all
patterns that you use when you want to communicate outside
your particular circle of colleagues.
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) Given a sample with the format of the UNIX date string
local to California, create a SPICE time picture for use
in timout_c.
Using that SPICE time picture, convert a series of ephemeris
times to that picture format.
Use the LSK kernel below to load the leap seconds and time
constants required for the conversions.
naif0012.tls
Example code begins here.
/.
Program timout_ex1
./
#include <stdio.h>
#include "SpiceUsr.h"
int main( )
{
/.
Local parameters.
./
#define ERRLEN 400
#define TIMLEN 65
/.
Local variables
./
SpiceBoolean ok;
SpiceChar err [ERRLEN];
SpiceChar pictur [TIMLEN];
SpiceChar * sample;
SpiceChar timstr [TIMLEN];
SpiceChar * utcstr;
SpiceDouble et;
/.
Load LSK file.
./
furnsh_c ( "naif0012.tls" );
/.
Create the required time picture.
./
sample = "Thu Oct 01 11:11:11 PDT 1111";
tpictr_c ( sample, ERRLEN, TIMLEN, pictur, &ok, err );
if ( ! ok )
{
printf( "Invalid time picture.\n" );
printf( "%s\n", err );
}
else
{
/.
Convert the input UTC time to ephemeris time.
./
utcstr = "24 Mar 2018 16:23:00 UTC";
str2et_c ( utcstr, &et );
/.
Now convert `et' to the desired output format.
./
timout_c ( et, pictur, TIMLEN, timstr );
printf( "Sample format: %s\n", sample );
printf( "Time picture : %s\n", pictur );
printf( "\n" );
printf( "Input UTC : %s\n", utcstr );
printf( "Output : %s\n", timstr );
}
return ( 0 );
}
When this program was executed on a Mac/Intel/cc/64-bit
platform, the output was:
Sample format: Thu Oct 01 11:11:11 PDT 1111
Time picture : Wkd Mon DD HR:MN:SC PDT YYYY ::UTC-7
Input UTC : 24 Mar 2018 16:23:00 UTC
Output : Sat Mar 24 09:23:00 PDT 2018
2) Convert a UTC time to a string that contains both the
calendar representations of the date as well as the Julian
date; for example a string of the form:
"Thu Aug 01 09:47:16 PDT 1996 (2450297.1994 JDUTC)"
Use the LSK kernel below to load the leap seconds and time
constants required for the conversions.
naif0012.tls
Example code begins here.
/.
Program timout_ex2
./
#include <stdio.h>
#include "SpiceUsr.h"
int main( )
{
/.
Local parameters.
./
#define TIMLEN 80
/.
Local variables
./
SpiceChar * pictur;
SpiceChar timstr [TIMLEN];
SpiceChar * utcstr;
SpiceDouble et;
/.
Load LSK file.
./
furnsh_c ( "naif0012.tls" );
/.
Convert the input UTC time to ephemeris time.
./
utcstr = "24 Mar 2018 16:23:00 UTC";
str2et_c ( utcstr, &et );
/.
Create the required time picture. This could be done
using tpictr_c.
./
pictur = "Wkd Mon DD HR:MN ::UTC-7 YYYY (JULIAND.#### JDUTC)";
/.
Now convert `et' to the desired output format.
./
timout_c ( et, pictur, TIMLEN, timstr );
printf( "Input UTC: %s\n", utcstr );
printf( "Output : %s\n", timstr );
return ( 0 );
}
When this program was executed on a Mac/Intel/cc/64-bit
platform, the output was:
Input UTC: 24 Mar 2018 16:23:00 UTC
Output : Sat Mar 24 09:23 2018 (2458202.1826 JDUTC)
RestrictionsNone. Literature_ReferencesNone. Author_and_InstitutionN.J. Bachman (JPL) J. Diaz del Rio (ODC Space) E.D. Wright (JPL) Version
-CSPICE Version 1.2.0, 10-AUG-2021 (EDW) (JDR) (NJB)
Changed the input argument name "lenout" to "outlen" for
consistency with other routines.
Corrected typo preventing correct calculation of decimal
values for HR.###... and MN.###... markers with ::UTC+N:M
and ::UTC-N:M meta tags.
Added "::TT" as a time system meta marker equivalent-to/
alias-for "::TDT". No change to functionality.
Edited the header to comply with NAIF standard. Converted the
existing code fragments into complete examples and added
references to required LSKs.
Updated -Exceptions section, rewording the existing entry
and adding three additional cases. Fixed call to tpictr_c in
-Particulars.
Corrected header example string: changed token HH to HR.
Updated "output" argument description in -Detailed_Output.
-CSPICE Version 1.1.1, 14-AUG-2006 (EDW)
Edited incorrect description of output. Replace mention of
ldpool_c with furnsh_c.
-CSPICE Version 1.1.0, 09-FEB-1998 (NJB)
Re-implemented routine without dynamically allocated, temporary
strings. Updated the -Exceptions header section.
-CSPICE Version 1.0.0, 25-OCT-1997 (EDW)
Index_EntriesConvert and format d.p. seconds past J2000 as a string |
Fri Dec 31 18:41:14 2021