back_end

 $self->back_end( 'DateTime::Calendar::Christian' );
 $self->back_end( 'Christian' );
 $self->back_end( 'Christian,reform_date=uk' );
 $self->back_end( 'Christian', reform_date => 'uk' );
 
 my $back_end = $self->back_end();
 my ( $class, @arg ) = $self->back_end();

This method acts as both accessor and mutator for the back end class that does all the actual time formatting.

When called with arguments it is a mutator, setting the name of the back end class, and any arguments that need to be passed to its "new()" method. The class specified should conform to the DateTime interface. If the class name begins with 'DateTime::Calendar::', this can be omitted as in the second example above. Arguments can be specified as comma-delimited 'name=value' pairs, as in the third example, or as separate name/value arguments, as in the fourth example.

When called with no arguments this method is an accessor. If called in list context it returns the class name and argument/value pairs as separate items. If called in scalar context the arguments are concatenated to the class name as comma-delimited 'name=value' pairs.

__preprocess_strftime_format

 my $mod = $self->__preprocess_strftime_format( $dt_obj, $fmt );

The functionality documented below is supported, but this method is not, and may be changed or revoked without notice at any time. This method will in fact throw an exception unless called from a subclass of this class.

This package-private method pre-processes a format, finding and potentially replacing substrings that look like '%{name:modifiers}'. This is a further extension of the DateTime extension, providing more control of the output.

The arguments are a DateTime or "DateTime-ish" object and the format that is to be pre-processed. The return is the pre-processed format.

In the substrings that are (potentially) replaced, the 'name' represents either a special-case string or the name of a method on the $dt_obj object. If it is neither, the substring is left unmodified. The special-case names are:

%

This causes a literal '%' to be inserted.

calendar_name

This causes either 'Gregorian' or 'Julian' to be inserted. You get 'Julian' only if $dt_obj has an "is_julian()" method, and that method returns a true value. Otherwise, if the class name of the back end object begins with 'DateTime::Calendar::' you get the shortened name. Otherwise you get 'Gregorian'. There is no provision for localization, unfortunately.

The colon and modifiers are optional. If present, the modifiers consist of, in order:

zero or more single-character flags;

These modify the formatting of the value, and may appear in any order. The following flags are implemented:

a field width.

This is a non-negative integer, not beginning with zero, which specifies the width of the output. Output will be at least this width, but may be wider unless the 't' flag was specified.

For example, if the $dt_obj represents the Ides of March, 44 BC, and the template is '%{year_with_christian_era:06}-%m-%d', the returned value will be '0044BC-%m-%d'.

 $dt_obj->strftime(
     $self->__preprocess_strftime_format(
         $dt_obj, '%{year_with_christian_era:06}-%m-%d' ) );

would therefore produce '0044BC-03-15'.