The "From" pair of fields tells CHRONOS in which time System/Type the input time is specified; the "To" pair tells CHRONOS to which time System/Type it should be converted; CHRONOS supports the following time systems:
The following time types are supported for the UTC system:
All of the above time types are supported ET time types. Also available is:
The following time types are supported for the SCLK system:
3/1248531085.006
1248543443
1437200032:006:23
4A8ADDCA:48
4A2A34BB
2/4A8A5052.48.1A
The following time types are supported for the LST system:
SOL 12 12:00:01
SOL 132 01:22:32.498
SOL 2 9
UTC/(SCET,ERT,ETT) and ET/(SCET,ERT,ETT) times used as input must be provided as time strings that can be parsed by the SPICE STR2ET routine. Below is an extract from the STR2ET subroutine header, explaining acceptable formats and providing some examples.
The variety of ways people have developed for representing
times is enormous. It is unlikely that any single subroutine
can accommodate the wide variety of custom time formats that
have arisen in various computing contexts. However, we
believe that this routine will correctly interpret most time
formats used throughout the planetary science community.
For example this routine supports ISO time formats, UNIX
`date` output formats, VMS time formats, MS-DOS formats,
etc. One obvious omission from the strings recognized by
this routine are strings of the form
93234.1829 or 1993234.1829
Some readers may recognize this as the epoch that is 0.1829
days past the beginning of the 234'th day of 1993. However,
other readers may regard this interpretation as a bit
obscure.
Below we outline some of the rules used in the interpretation
of strings. A more complete discussion of the interpretation
of strings is given in the routine TPARTV.
Default Behavior
----------------
Consider the string
1988 June 13, 3:29:48
There is nothing in this string to indicate what time system
the date and time belong to. Moreover, there is nothing to
indicate whether the time is based on a 24-hour clock or
twelve hour clock.
In the absence of such indicators, the default interpretation
of this string is to regard the time of day to be a time on
a 24-hour clock in the UTC time system. The date is a date
on the Gregorian Calendar (this is the calendar used in nearly
all western societies).
Labels
------
If you add more information to the string, STR2ET can then
make a more informed interpretation of the time string.
For example:
1988 June 13, 3:29:48 P.M.
is still regarded as a UTC epoch. However, with the addition
of the 'P.M.' label it is now interpreted as the same epoch
as the unlabeled epoch 1988 June 13, 15:29:48. Similarly
1988 June 13, 12:29:48 A.M.
is interpreted as
1988 June 13, 00:29:48
For the record: 12:00 A.M. corresponds to Midnight (00:00 on the
24 hour clock. 12:00 P.M. corresponds to Noon. (12:00) on the
24 hour clock.
You may add still further indicators to the string. For example
1988 June 13, 3:29:48 P.M. PST
is interpreted as an epoch in the Pacific Standard Time system.
This is equivalent to
1988 June 13, 07:29:48 UT
The following U.S. time zones are recognized.
EST --- Eastern Standard Time ( UTC-5:00 )
CST --- Central Standard Time ( UTC-6:00 )
MST --- Mountain Standard Time ( UTC-7:00 )
PST --- Pacific Standard Time ( UTC-8:00 )
EDT --- Eastern Daylight Time ( UTC-4:00 )
CDT --- Central Daylight Time ( UTC-5:00 )
MDT --- Mountain Daylight Time ( UTC-6:00 )
PDT --- Pacific Daylight Time ( UTC-7:00 )
Any other time zone may be specified by
representing its offset from UTC.
This notation starts with the letters 'UTC' followed by a
'+' for time zones east of Greenwich and '-' for time zones
west of Greenwich. This is followed by the number of hours
to add or subtract from UTC. This is optionally followed
by a colon ':' and the number of minutes to add or subtract
to get the local time zone. Thus to specify the time zone of
Calcutta (which is 5 and 1/2 hours ahead of UTC) you would
specify the time zone to be UTC+5:30. To specify the time zone
of Newfoundland (which is 3 and 1/2 hours behind UTC) use the
offset notation UTC-3:30.
For the Record: Leapseconds occur at the same time in all
time zones. In other words, the seconds component of a time
string is the same for any time zone as is the seconds
component of UTC. Thus the following are all legitimate
ways to represent an epoch of some event that occurred
in the leapsecond
1995 December 31 23:59:60.5 (UTC)
1996 January 1, 05:29:60.5 (UTC+5:30 --- Calcutta Time)
1995 December 31, 20:29:60.5 (UTC-3:30 --- Newfoundland)
1995 December 31 18:59:60.5 (EST)
1995 December 31 17:59:60.5 (CST)
1995 December 31 16:59:60.5 (MST)
1995 December 31 15:59:60.5 (PST)
In addition to specifying time zones, you may specify
that the string be interpreted as a formal calendar
representation in either the Barycentric Dynamical Time system
(TDB) or the Terrestrial Dynamical Time system (TDT). In
These systems there are no leapseconds. Times in TDB
are written as
1988 June 13, 12:29:48 TDB
TDT times are written as:
1988 June 13, 12:29:48 TDT
Finally, you may explicitly state that the time system is UT
1988 June 13, 12:29:48 UTC.
Note that you may not specify two different time systems
simultaneously. For example
1988 June 13, 12:29:48 PDT TDT
You might be able to make some kind of reasonable guess as
to the meaning of this string, but we've decided to regard
such strings as errors.
Abbreviating Years
------------------
Although it can lead to confusion, many people are in the
habit of abbreviating years when they write them in dates.
For example
99 Jan 13, 12:28:24
Upon seeing such a string, most of us would regard this
as being 1999 January 13, 12:28:24 and not January 13 of
the year 99. This routine interprets years that are less
than 100 as belonging either to the 1900's or 2000's. Years
greater than 68 ( 69 - 99 ) are regarded as being an
abbreviation with the '19' suppressed (1969 - 1999). Years
smaller than 69 ( 00 - 68 ) are regarded as being an
abbreviation with the '20' suppressed (2000 - 2068).
Note that in general it is usually a good idea to write
out the year. Or if you'd like to save some typing
abbreviate 1999 as '99.
If you need to specify an epoch whose year
is less than 1000, we recommend that you specify the era
along with the year. For example if you want to specify
the year 13 A.D. write it as
13 A.D. Jan 12
When specifying the era it should immediately follow the year.
Both the A.D. and B.C. eras are supported.
Changing Default Behavior
-------------------------
As discussed above, if a string is unlabelled, it is regarded
as representing a string in the UTC time system on the
Gregorian calendar. Abbreviated years are
regarded as abbreviations of the years from 1969 to 2068.
You may modify these defaults through the routines TIMDEF
and TSETYR (an entry point of TEXPYR).
You may:
Set the calendar to be Gregorian, Julian or a mixture of
the two using TIMDEF;
Set the time system to be UTC, TDB, TDT or any time zone
using TIMDEF;
Set the range of year abbreviations to be any 100 year
interval using TSETYR.
See the routines TEXPYR and TIMDEF for details on changing
defaults.
These alterations affect only the interpretation of unlabelled
strings. If an input string is labelled the specification
in the label is used.
If some component of a date or time is "out-of-range" STR2ET
regards the string as erroneous. Below is a list of
erroneous strings and why they are regarded as such.
1997 Jan 32 12:29:29 --- there are only 31 days in January
'98 Jan 12 13:29:29 A.M. --- Hours must be between 1 and 12
inclusive when A.M. or P.M. is
specified.
1997 Feb 29, 12:29:20.0 --- February has only 28 days in
1997. This would be ok if the
year was 1996.
1992 Mar 12 12:62:20 --- Minutes must be between 0 and 59
inclusive.
1993 Mar 18 15:29:60.5 --- Seconds is out of range for this
date. It would not be out of
range for Dec 31 23:59:60.5 or
Jun 30 23:59:60.5 because these
can be leapseconds (UTC).
Specifics On Interpretation of the Input String
-----------------------------------------------
The process of examining the string to determine its meaning
is called "parsing" the string. The string is parsed by first
determining its recognizable substrings (integers, punctuation
marks, names of months, names of weekdays, time systems, time
zones, etc.) These recognizable substrings are called the
tokens of the input string. The meaning of some tokens are
immediately determined. For example named months, weekdays and
time systems have clear meanings. However, the meaning of
a numeric component must be deciphered from its magnitude
and location in the string relative to the immediately recognized
components of the input string.
To determine the meaning of the numeric tokens in the input
string, a set of "production rules" and transformations are
applied to the full set of tokens in the string. These
transformations are repeated until the meaning of every token
has been determined or until further transformations yield
no new clues into the meaning of the numeric tokens.
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. STR2ET does not
support such strings.
No exponential components are allowed. For example you
can't input 1993 Jun 23 23:00:01.202E-4 you have
to explicitly list all zeros that follow the decimal
point: i.e. 1993 Jun 23 23:00:00.0001202
5) The single colon (:) when used to separate numeric
components of a string is interpreted as separating
Hours, Minutes, and Seconds of time.
6) If a double slash (//) or double colon (::) follows
a pair of integers, those integers are assumed to
represent the year and day of year.
7) 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 TEXPYR
for further discussion of abbreviated years.
8) An integer followed by 'B.C.' or 'A.D.' is regarded as
a year in the era associated with that abbreviation.
9) All dates are regarded as belonging to the extended
Gregorian Calendar (the Gregorian calendar is the calendar
currently used by western society). See the routine TIMDEF
to modify this behavior.
10) If the International Standard Organization (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.
11) 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, forward
slash, period, day of year mark "//" or "::" )
Note the delimiters do not have to be the same. The pair
of characters ",-" counts as two successive delimiters.
12) White space and commas serve only to delimit tokens in the
input string. They do not affect the meaning of any
of the tokens.
13) If an integer is greater than 1000 (and the 'JD' label
is not present, the integer is regarded as a year.
14) 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.
Examples
--------
Below is a sampling of some of the time formats that
are acceptable as inputs to STR2ET and the way they
are interpreted. A complete discussion
of permissible formats is given in the SPICE routine
TPARTV as well as the reference file time.req
located in the /doc directory of the toolkit. "na"
means Not Applicable.
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
1995-08T18:28:12 1995 na 008 na 18 28 12
1995-18T 1995 na 018 na 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 --- Seconds
* The default interpretation of a year that has been abbreviated
with a leading quote as in 'xy (such as '92) is to treat
the year as 19xy if xy > 68 and to treat it is 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 SPICE routine TSETYR which is an entry point in
the SPICE module TEXPYR. 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.
+ 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.
...
UTC/(SCET,ERT,ETT) and ET/(SCET,ERT,ETT) times output from CHRONOS are formatted as time string in accordance with the format picture specification recognized by SPICE's TIMOUT routine. Below is an extract from the TIMOUT subroutine header, explaining acceptable specifications of output format pictures and providing some examples.
A format picture is simply a string of letters that lets
TIMOUT 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 as
represented a two digit integer, another colon, and seconds
rounded to 4 decimal places and having a two digit integer
part. This is followed by a space and the string (TDB). The
special marker `::TDB' in the time picture is an
``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 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 represent 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 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.') giving
era associated with an epoch.
'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 uses the
values returned by the SPICE routine TIMDEF. The default
time system, calendar returned by TIMDEF are UTC and
the Gregorian calendar. The default time zone returned
by TIMDEF is a blank indicating that no time zone offset
should be used.
See the header for the routine TIMDEF 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 can produce output strings for epochs relative to
any of the three systems UTC, TDT, or TDB. If you do not
explicitly specify a time system, TIMOUT will produce strings
relative to the time system returned by the SPICE routine
TIMDEF. Unless you call TIMDEF and change it, the default time
system is UTC. However, by using one of the Meta Markers
::UTC, ::TDT, or ::TDB you may specify that TIMOUT produce
time strings relative to the UTC, TDT, or TDB system
respectively.
Time Zones
The meta markers ::UTC+h:m and ::UTC-h:m allow you
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 ::UT
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 strings such as
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 uses the default calendar returned by TIMDEF.
Under most circumstances this will be the Gregorian calendar
(::GCAL). However you may specify that TIMOUT use a specific
calendar through use of one of the calendar Meta Markers. You
may specify that TIMOUT 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 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 with this string, and it will create
the appropriate PICTUR for use with TIMOUT.
CALL TPICTR ( 'Fri Jul 26 12:22:09 PDT 1996', PICTUR, OK )
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. For example, you might be able to understand
that 19960212121116 is Feb 2 1996, 12:11:16. However,
TPICTR cannot recognize this string. Thus it is important
to check the logical output OK to make sure that TPICTR was
able to understand the time picture you provided.
Even thought TPICTR 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.
...
On output UTC/LT, ET/(LT,SECONDS) and LST/LSUN are formatted as DP numbers in accordance with a format picture specification recognized by SPICE's DPFMT routine. Below is an extract from the DPFMT subroutine header explaining acceptable specifications of an output DP format picture and providing some examples.
Format Picture Construction Rules
---------------------------------
A format picture is a string used to describe the format of
the output string. There are four special characters
recognized by DPFMT --- a leading + or -, a leading
zero ( '0' ) or a zero that follows a leading + or -,
and the first decimal point of the string.
All other non-blank characters are regarded as
equivalent. The picture ends at the first blank
character. The effects associated with the various
characters in a picture are spelled out in the
description of the output STRING.
The following pictures are treated as errors.
' ', '+', '-', '.', '+.', '-.'
If the first character of the picture is a minus sign,
the first character in the output string will be
a blank if the number is non-negative, a minus sign
if the number is negative.
If the first character of the picture is a plus sign,
the first character of the output string will be a
plus if the number is positive, a blank if the number
is zero, and a minus sign if the number is negative.
If the first character of the string is NOT a sign
(plus or minus) the first character of the output
string will be a minus sign if the number is negative
and will be the first character of the integer part
of the number otherwise.
The integer portion of STRING will contain the same
number of characters as appear before the decimal point
(or last character if there is no decimal point) but
after a leading + or -.
If the picture begins with any of the following
'+0', '-0', or '0'
it is said to have a leading zero. If a picture has
a leading zero and the integer portion is not large
enough to fill up the integer space specified by
PICTUR, STRING will be zero padded from the sign (if
one is required) up to the first character of the
integer part of the number.
If picture does NOT have a leading zero and
the integer portion is not large enough to fill up
the space specified by PICTUR, STRING will be blank
padded on the left between the sign (if one is required)
and the first character of the integer part of the
number.
If a decimal point ( '.' ) is present in PICTUR it
will be present following the integer portion of
STRING. Moreover, the decimal portion of STRING will
contain the same number of digits as there are
non-blank characters following the decimal point in
PICTUR. However, only the first 14 digits starting
with the first non-zero digit are meaningful.
If the format specified by PICTUR does not provide
enough room for the integer portion of X, the routine
determines whether or not the number of characters
present in the picture is sufficient to create a
representation for X using scientific notation. If
so, the output is displayed using scientific notation
(leading signs if they are present in PICTUR, will
also appear in STRING). If the format specified
by PICTUR is too short to accommodate scientific
notation, the output string is filled with '*' to
the same length as the length of PICTUR. Leading
signs are not preserved in this overflow case.
Examples
--------
Suppose that X has the binary representation of PI.
Then the table below illustrates the strings that
would be produced by a variety of different pictures.
PICTUR | STRING
-------------------------------
'0x.xxx' | '03.142'
'xx.xxx' | ' 3.142'
'+xxx.yyyy' | '+ 3.1416'
'-.yyyy' | '******'
'xxxxxxxx' | ' 3'
'00xx' | '0003'
'-00.0000000' | ' 03.1415927'
'00' | '03'
'x.' | '3.'
'.mynumber' | '3.142E+00'
'my dog spot' | ' 3'
'my.dog spot' | ' 3.142'
'+my.dog,spot' | '+ 3.14159265'
Suppose that X has the binary representation of 2/3.
Then the table below illustrates the strings that
would be produced by a variety of different pictures.
PICTUR | STRING
-------------------------------
'+x.xxx' | '+0.667'
'+xx.xxx' | '+ 0.667'
'xxx.yyyy' | ' 0.6667'
'.yyyy' | '.6667'
'xxxxxxxx' | ' 1'
'00xx' | '0001'
'-0.0000000' | ' 0.6666667'
'00' | '01'
'x.' | '1.'
'mynumber' | ' 1'
'my dog spot' | ' 1'
'my.dog spot' | ' 0.667'
'my.dog,spot' | ' 0.66666667'
Suppose that X has the binary representation of
-8/9. Then the table below illustrates the strings
that would be produced by a variety of different
pictures.
PICTUR | STRING
-------------------------------
'+x.xxx' | '-0.889'
'-00.xxxx' | '-00.8889'
'xxx.xxx' | ' -0.889'
'000.000' | '-00.889'