Usage document for %form-date.r

Introduction to %form-date.r

This library script is for inclusion in other programs and allows
sophisticated date formatting, ala strftime, but not exactly

form-date At a Glance

>> form-date now "%A %e%i %B, %Y at %T"
== "Thursday 26th April, 2007 at 00:44:12"

>> form-date now "%d-%b-%Y/%H:%M:%S%Z"
== "26-Apr-2007/00:49:39-04:00"

>> now
== 26-Apr-2007/0:52:13-4:00

>> form-date now/precise "%c"
== "19-Jul-2007/00:01:45.108242-04:00"

Using %form-date.r

Including this function is simple. Just DO it.

>> do %form-date.r

or to execute this right out of the rebol.org library

>> do http://www.rebol.org/download-a-script.r?script-name=form-date.r

You now have the form-date function

>> help form-date
USAGE:
    FORM-DATE date format /gmt

DESCRIPTION:
     Renders a date to a given format (largely compatible with strftime)
     FORM-DATE is a function value.

ARGUMENTS:
     date -- (Type: date)
     format -- (Type: any-string)

REFINEMENTS:
     /gmt -- Align time with GMT

The format string

Ordinary characters placed in the format string are inserted into return value without conversion.
Conversion specifications are introduced by a % character, and terminated by a conversion
specifier character, and are replaced and inserted into return value as follows:

%a The abbreviated weekday name according to the current locale.
%A The full weekday name according to the current locale.
%b The abbreviated month name according to the current locale.
%B The full month name according to the current locale.
%c The preferred date and time representation for the current locale. In this case the locale is REBOLand, with a little %b mixed in.
%C The century number (year/100) as a 2-digit integer.
%d The day of the month as a decimal number (range 01 to 31).
%D Equivalent to %Y/%m/%d.
%e Like %d, the day of the month as a decimal number, without a leading zero.
%G The ISO 8601 year with century as a decimal number. The 4-digit year corresponding to the ISO week number (see %V). This has the same format and value as %y, except that if the ISO week number belongs to the previous or next year, that year is used instead.
%g Like %G, but without century, i.e., with a 2-digit year (00-99).
%H The hour as a decimal number using a 24-hour clock (range 00 to 23).
%i The english suffix for numeric value, “st” for 01, “th” for 04.
%I The hour as a decimal number using a 12-hour clock (range 01 to 12).
%j The day of the year as a decimal number (range 001 to 366).
%J Like %j, but without leading zeroes.
%m The month as a decimal number (range 01 to 12).
%M The minute as a decimal number (range 00 to 59).
%p Either “”AM”” or “”PM”” according to the given time value. Noon is treated as “”PM” and midnight as “”AM”.
%s The second as a decimal number 00-60 with REBOL nanosecond precision, a period followed by 6 digits.
%S The second as a decimal number (range 00 to 60). (The range is up to 60 to allow for occasional leap seconds.)
%t A tab character.
%T The time in 24-hour notation (%H:%M:%S).
%u The day of the week as a decimal, range 1 to 7, Monday being 1. See also %w.
%U The week number of the current year as a decimal number, range 00 to 53, starting with the first Sunday as the first day of week 01. See also %V and %W.
%V The ISO 8601:1988 week number of the current year as a decimal number, range 01 to 53, where week 1 is the first week that has at least 4 days in the current year, and with Monday as the first day of the week. See also %U and %W.
%w The day of the week as a decimal, range 0 to 6, Sunday being 0. See also %u.
%W The week number of the current year as a decimal number, range 00 to 53, starting with the first Monday as the first day of week 01.
%y The year as a decimal number without a century (range 00 to 99).
%Y The year as a decimal number including the century.
%Z The time-zone as hour offset from GMT.
%% A literal “”%”” character.

What you can learn

The interpolate function, along with date-codes is
an excellent example of parse. The dialect created is the two character
format specifiers that produce the date and time pieces. A strftime dialect.

REBOL can emulate the functionality of other systems, while still remaining REBOL.

REBOL code can look world-class elegant when properly formatted and factored.

What you can break

The date! parameter has to be a date!. If you use any time related format specifiers, it
has to be a date! that includes time information or returned fields may be incorrect.

>> form-date now/date "%T"
== "00:00:00"

>> form-date now/time "%T"
 Script Error: form-date expected date argument of type: date
 Near: form-date now/time "%T"

>> form-date now "%T"
== "02:29:39"

What’s new

With the addition of %c, you have clean, always the same length REBOL time-stamps.

>> 01-Jan-0001/00:00:00.000000-00:00
== 1-Jan-0001/0:00
>> form-date 01-Jan-0001/00:00:00.000000-00:00 "%c"
== "01-Jan-0001/00:00:00.000000+00:00"

>> form-date now/precise "%c"
== "19-Jul-2007/00:42:53.586560-04:00"

>> form-date now "%c"
== "19-Jul-2007/00:43:19.000000-04:00"

Precision versus Accuracy

Please note that now/precise while reporting 6 digit precision for the sub-seconds, is only as accurate as your computer clock will allow.

Credits

  • %form-date.r original author: Christopher Ross-Gill
  • Part of QuarterMaster, %qm.r by Christopher Ross-Gill http://www.ross-gill.com/
  • Usage document by Brian Tiffin, Library Team Apprentice, 23-Oct-2017