NoSQL operator: gregorian

Translates selected date columns from Julian to calendar format.

Usage: gregorian [options] [column ...]

Options:
    --input (-i) 'file'
      Read input from 'file' instead of STDIN.

    --output (-o) 'file'
      Write output to 'file' instead of STDOUT.

    --no-header (-N)
      Strip header from output.

    --last (-l)
      If the input table contains duplicated column names
      pick the last occurrence of each. The default is to
      pick the first one. This is sometimes useful after
      the 'jointable' operator.

    --short (-S)
      The year is expressed in two-digit format.

    --computer (-c)
      Output date format: yyyymmdd

    --iso (-I)
      Output date format: yyyy-mm-dd

    --europe (-e)
      Output date format: dd.mm.yyyy

    --us (-u)
      Output date format: mm/dd/yyyy

    --separator (-s) 's'
      Use 's' for the separator character in output dates,
      as opposed to the default '.' and '/'

    --help (-h)
      Display this help text.

Notes:

This program converts Julian dates in selected columns to Gregorian.
It is used together with "julian" to perform math on dates.

References:

1. http://aa.usno.navy.mil/faq/docs/JD_Formula.html

2. Fliegel, H. F. and van Flandern, T. C. (1968).
   Communications of the ACM, Vol. 11, No. 10 (October, 1968).

For example, let's suppose we have the following table:

$ cat date.rdb
Date
----
20011010

Here's how to compute the date corresponding to 100 days after
20011010:

julian Date < date.rdb |
  compute 'Date=sprintf("%f",Date+100)' |
  gregorian Date

Date
----
20020118

Note that we must instruct 'compute' not to switch to scientific
output notation. Without the sprintf(), simply doing a 'Date+=100'
would produce 2.45229e+06, which would then cause 'gregorian' to
compute a wrong date, due to insufficient precision in the output of
'compute'.