NAME

       convcal - convert dates to different formats

SYNOPSIS

       convcal [OPTIONS] [DATE]

DESCRIPTION

       convcal  is  part  of  the grace software package, an application for two-dimensional data visualization.
       convcal converts dates from and to various formats. The  following  date  formats  are  supported  (hour,
       minutes and seconds are always optional):

       iso    1999-12-31T23:59:59.999

       european
              31/12/1999 23:59:59.999 or 31/12/99 23:59:59.999

       us     12/31/1999 23:59:59.999 or 12/31/99 23:59:59.999

       days   123456.789

       seconds
              123456.789

       The  formats  are  tried  in  the  following  order  :  users's choice, iso, european and us (there is no
       ambiguity between calendar formats and numerical formats and therefore no order is specified for them).

USAGE

       convcal reads the dates either on the command line or in the standard input if the command line  contains
       no date.

       The  user's  choice  for the input format put one format before the other ones in the trial list, this is
       mainly useful for US citizen which would certainly prefer to  have  US  format  checked  before  european
       format. The default user's choice (nohint) does nothing so the following formats of the list are checked.

       The  separators between various fields can be any characters in the set: " :/.-T". One or more spaces act
       as one separator, other characters can not be repeated, the T separator is allowed only between date  and
       time,  mainly  for  iso8601.  So the string "1999-12 31:23-59" is allowed (but not recommended).  The '-'
       character is used both as a separator (it is traditionally used in iso8601 format) and as the unary minus
       (for dates in the far past or for numerical dates). When the year is between 0 and 99 and is written with
       two or less digits, it is mapped to the era beginning at wrap year and  ending  at  wrap  year  +  99  as
       follows :

       [wy ; 99] -> [ wrap_year ; 100*(1 + wrap_year/100) - 1 ]

       [00 ; wy-1] -> [ 100*(1 + wrap_year/100) ; wrap_year + 99]

       so for example if the wrap year is set to 1950 (which is the default value), then the mapping is :

       range [00 ; 49] is mapped to [2000 ; 2049]

       range [50 ; 99] is mapped to [1950 ; 1999]

       this is reasonably Y2K compliant and is consistent with current use.  Specifying year 1 is still possible
       using more than two digits as follows : "0001-03-04" is unambiguously March the 4th, year 1, even if  the
       user's  choice  is  us  format. However using two digits only is not recommended (we introduce a 2050 bug
       here so this feature should be removed at some point in the future ;-)

       Numerical dates (days and seconds formats) can be specified using integer, real  or  exponential  formats
       (the  'd'  and  'D'  exponant  markers  from fortran are supported in addition to 'e' and 'E').  They are
       computed according to a customizable reference date.  The default value is given by the REFDATE  constant
       in  the  source  file.   You can change this value as you want before compiling, and you can change it at
       will  using  the  -r  command  line  option.   The   default   value   in   the   distributed   file   is
       "-4713-01-01T12:00:00",  it  is  a classical reference for astronomical events (note that the '-' is used
       here both as a unary minus and as a separator).

       The program can be used either for Denys's and gregorian calendars. It does not take  into  account  leap
       seconds  :  you can think it works only in International Atomic Time (TAI) and not in Coordinated Unified
       Time (UTC) ...  Inexistant dates are  detected,  they  include  year  0,  dates  between  1582-10-05  and
       1582-10-14, February 29th of non leap years, months below 1 or above 12, ...

OPTIONS

       A summary of the options supported by convcal is included below.

       -h     prints the help message on stderr and exits successfully

       -i format
              set  user's  choice  for  input format, supported formats are iso, european, us, days, seconds and
              nohint.  At the beginning the input format is nohint, which means the program  try  to  guess  the
              format by itself, if the user's choice does not allow to parse the date, other formats are tried

       -o format
              force  output  format,  supported formats are iso, european, us, days, seconds and nohint.  At the
              beginning, the output format is nohint, which means the program uses days format for dates read in
              any calendar format and uses iso8601 for dates read in numerical format

       -r date
              set  reference  date  (the  date  is  read  using  the  current input format) at the beginning the
              reference is set according to the REFDATE constant in the code, which is  -4713-01-01T12:00:00  in
              the distributed file.

       -w year
              set the wrap year to year

SEE ALSO

       grace(1)

       http://plasma-gate.weizmann.ac.il/Grace/

AUTHOR

       Luc Maisonobe

       This  man-page  was  written by Jan Schaumann <jschauma@netmeister.org> as part of "The Missing Man Pages
       Project".  Please see http://www.netmeister.org/misc/m2p2/index.html for details.