DateTime::Fiscal::Year - Calculate the day or week of the Fiscal Year with an arbitrary start date

  use DateTime;
  use DateTime::Fiscal::Year;

  my $dt = DateTime->new(year=>2003, month=>02, day=>01);
  my $dt2 = DateTime->new(year=>2003, month=>03, day=>01);

  my $fiscal = DateTime::Fiscal::Year->new( start => $dt );

  $fiscal->day_of_fiscal_year( $dt2 );

	or

  $fiscal->week_of_fiscal_year( $dt2 );

	or

  $fiscal->period_of_fiscal_year( 12, $dt2 );

	or 

  $fiscal->quarter_fiscal_year( 13, $dt2 );

package DateTime::Fiscal::Year;

use strict;

use DateTime;
use Params::Validate qw( validate validate_pos);
use vars qw($VERSION);

$VERSION = '0.02';

my ( @MonthLengths, @LeapYearMonthLengths );

BEGIN {
	@MonthLengths =
		( 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31 );

	@LeapYearMonthLengths = @MonthLengths;
	$LeapYearMonthLengths[1]++;
}

sub new {
	my $class = shift;
	my %args = validate( @_, { start => { isa => 'DateTime' } });

	my $self = { start => $args{start} };
	bless $self, $class;
	return $self;
}


sub day_of_fiscal_year {
	my $self = shift;

#	return $self->{day_of_fiscal_year} if defined($self->{day_of_fiscal_year});

	my @args = validate_pos( @_,  { isa => 'DateTime' } );
	my $dofy;

	my $offset = ($self->{start}->day_of_year);

	my $dify = ( $self->{start}->is_leap_year ? 366 : 365 );	
	my $doy	= $args[0]->day_of_year;	

	if ( $doy >= $offset ) { $dofy = ( $doy - $offset + 1  ); } else { $dofy = (( $dify - $offset) + $doy + 1); }
	$self->{day_of_fiscal_year} = $dofy;
}

sub week_of_fiscal_year {
	my $self = shift;
	
#	return $self->{week_of_fiscal_year} if defined($self->{week_of_fiscal_year});
	my @args = validate_pos( @_,  { isa => 'DateTime' } );

	my $wofy;

	$wofy = $self->day_of_fiscal_year( $args[0] ) / 7;
	$wofy = ( $wofy == int($wofy) ? $wofy : int($wofy + 1) );
	if ($wofy == 53 ) { $wofy = 52 ;}
	$self->{week_of_fiscal_year} = $wofy;
	 			
}

sub period_of_fiscal_year {
	my $self = shift;

#	return $self->{period_of_fiscal_year} if defined($self->{period_of_fiscal_year});

	$self->{number_of_fiscal_periods} = shift;
	my @args = validate_pos( @_,  { isa => 'DateTime' } );



	$self->_align_fiscal_periods;
	if ( $self->{number_of_fiscal_periods} == 12 ) {
		$self->{period_of_fiscal_year} = $self->_period_index( $args[0] );
		$self->{period_of_fiscal_year}++ if ( $self->{start}->month == 1 );
	}

	if ( $self->{number_of_fiscal_periods} == 13 ) {
		$self->{period_of_fiscal_year} = $self->{fiscal_periods}->[$self->week_of_fiscal_year( $args[0] )];
	}

	$self->{period_of_fiscal_year};
}

sub quarter_of_fiscal_year {
	my $self = shift;

	$self->period_of_fiscal_year( shift, shift );
	
	if ( $self->{number_of_fiscal_periods} == 12 ) { 
		return $self->{quarter_of_fiscal_year} = int((( $self->{period_of_fiscal_year} - 1)/3) + 1); 
	}

	if ( $self->{number_of_fiscal_periods} == 13 ) {
		return $self->{quarter_of_fiscal_year} = int((( $self->{period_of_fiscal_year} - 1)/4) + 1);
	}	
}

sub _align_fiscal_periods {
	my $self = shift;

	if ( $self->{number_of_fiscal_periods} == 12 ) {
		my @periods = $self->{start}->is_leap_year ? @LeapYearMonthLengths : @MonthLengths;
			for ( my $i = 1; $i < $self->{start}->month; $i++ ) {
				push @periods, shift @periods;
			}
		push @periods, 0;
		for ( my $i = 0; $i <= $#periods; $i++ ) {
			$periods[$i] += $periods[$i - 1];
		}
		unshift @periods, 0;
		$self->{fiscal_periods} = \@periods;
	};

	if ( $self->{number_of_fiscal_periods} == 13 ) {
		my @periods = 0;
		my $counter = 0;
		my $period_index = 1;

		for ( my $i = 1; $i <= 52; $i++, $counter++ ) {
			if ( $counter == 4 ) { $counter = 0; $period_index++; }
			$periods[$i] = $period_index;
		}
		$self->{fiscal_periods} = \@periods;
	}
	$self->{fiscal_periods};
}

sub _period_index {
	my $self = shift;

        foreach my $index ( reverse 1..12 ) {
            return $index
		if $self->{fiscal_periods}->[$index - 1] < $self->day_of_fiscal_year( @_ );
	}
}

1;

__END__