# file name: Date_Time.pm
# language: perl 5
# author: Rajiv Pant (Betul)   betul@rajiv.com   http://rajiv.org

# (c) 1996 Rajiv Pant (Betul)
# Feel free to use this without any obligations to me or anyone else.
# Version 1.02. 1996/May/28

# description:
#       Date and Time package


package Date_Time ;

require 5.002 ;

use strict ;

local ($[) = 0 ;        # start array index with 0 for this function
                        # just in case the program has it set to 1.
                

$Date_Time::author = <<'';
Rajiv Pant (Betul)   betul@rajiv.com   http://rajiv.org


$Date_Time::VERSION = 1.02 ;    # 1.02 Fixed minor bug in yr method



@Date_Time::month_names = qw { 

January         February        March           April
May             June            July            August
September       October         November        December

} ;



# three letter abbriviations for the names of the months

@Date_Time::months = @Date_Time::month_names ;
grep (s/^(\w{3}).*$/$1/, @Date_Time::months) ;




@Date_Time::names_of_days_of_week = qw {

Sunday          Monday          Tuesday         Wednesday
Thursday        Friday          Saturday

} ;


# three letter abbriviations for the names of the days of the week

@Date_Time::days_of_week = @Date_Time::names_of_days_of_week ;
grep (s/^(\w{3}).*$/$1/, @Date_Time::days_of_week) ;


1 ;     # The modules needs to retun a true value




# ---------------- functions ----------------

sub new
{
my $self = {} ;
my $class = shift ;

my $arg = shift ;


# TO DO: consider allowing multiple instead of using elsif
#       that will let people combine yesterday and last_year

if      ($arg =~ /yesterday/i)  { $self->{when} = -86400 ; }
elsif   ($arg =~ /tomorrow/i)   { $self->{when} = +86400 ; }
elsif   ($arg =~ /other.day[^\-\+\d]?([\+\-\d]+)/i)
  {
  $self->{when} = $1 * 86400 ;
  }
elsif   ($arg =~ /other.timestamp[^\-\+\d]?([\+\-\d]+)/i)
  {
  $self->{when} = $1 ;
  }
else
  {
  $self->{when} = 0 ;
  }

bless $self, $class ;
} # end of sub new







# public methods


sub version { $Date_Time::VERSION }



# the following methods return the day, month, year, hour, etc.


# the following year_short method returns the current year minus 1900
# it is the same as yr for dates less than the year 2000.
# it is better to use yr to get the last two digits of the year

# NOTE: this version of this library was written to deal with dates within
#       a few hunderd years around 1996. this interval is usually all that
#       my programs using this library need. i may add support for a wider
#       range in a later release if people request. don't worry about
#       future additions to this library -- they will not affect any of
#       the existing public methods that you use.


sub year_short
{
my $year_short = (&ctime)[5] ;
($year_short =~ /^\d\d(\d\d)$/) && ($year_short = $1) ;
$year_short ;
}



# returns all 4 digits of the year

sub year
{
my $year = &year_short + 1900 ;
}



# use this yr method to get the last two digits of the year

sub yr
{
my ($yr) = &year =~ /^\d\d(\d\d)$/ ;
$yr ;
}



# returns number of the month as one or two digits
# for eg. Sepetember is 9 October is 10

sub month_number_short
{
(&ctime)[4] + 1 ;       # adding one because array subscripts start at 0 here
}


sub month_number
{
my $month_number_short = &month_number_short ;
my $month_number = length ($month_number_short) == 1 ? 
   '0'. $month_number_short : $month_number_short ;
}



# returns name of the month abbriviated to three letters with the
# first letter uppercase and next two in lowercase. eg. Sep

sub month
{
$Date_Time::months[&month_number - 1] ;
                                # subtracting 1 because array subscripts
                                # start at 0 here
}


# full name of the month

sub month_name
{
$Date_Time::month_names[&month_number - 1] ;
                                # subtracting 1 because array subscripts
                                # start at 0 here
}





# returns the nth day of the year.
# eg. January 1 is day 1, February 2 is the day 33

sub nth_day_of_year
{
(&ctime)[7] ;
}




# returns the day of the month. days before the 10th are returned as
# a single digit

sub day_of_month_short
{
(&ctime)[3] ;
}



# same as day_of_month_short

sub today_short
{
&day_of_month_short ;
}




# returns two digits for the day of the month.
# days before the 10th begin with a 0 as in 09

sub day_of_month
{
my $today_short = &today_short ;
my $today = length ($today_short) == 1 ? '0'. $today_short : $today_short ;
}



# same as day_of_month

sub day
{
&day_of_month ;
}



# same as day_of_month

sub today
{
&day_of_month ;
}




# returns the number of the day of the week.
# eg. Sunday = 1, Saturday = 7

sub nth_day_of_week
{
(&ctime)[6] + 1 ;
}



# returns name of the day of the week abbriviated to three letters with the
# first letter uppercase and next two in lowercase. eg. Mon

sub day_of_week
{
$Date_Time::days_of_week[&nth_day_of_week - 1] ;
                                # subtracting 1 because array subscripts
                                # start at 0 here
}


# full name of the day of the week

sub day_of_week_name
{
$Date_Time::names_of_days_of_week[&nth_day_of_week - 1] ;
                                # subtracting 1 because array subscripts
                                # start at 0 here
}



# same as day_of_week_name

sub full_day_of_week
{
&day_of_week_name ;
}






# times of the day



sub hour { (&ctime)[2] ; }

# returns the hours as two digits

sub hh
{
my $hour = &hour ;
my $hh = length ($hour) == 1 ? '0'. $hour : $hour ;
}

sub hours { &hh ; }




sub minute { (&ctime)[1] ; }

# returns the minutes as two digits

sub mm
{
my $minute = &minute ;
my $mm = length ($minute) == 1 ? '0'. $minute : $minute ;
}

sub minutes { &mm ; }




sub second { (&ctime)[0] ; }

# returns the seconds as two digits
 
sub ss 
{
my $second = &second ;
my $ss = length ($second) == 1 ? '0'. $second : $second ;
}

sub seconds { &ss ; }







# some nicely formatted combinations


# eg. Saturday, March 16, 1996

sub date_format_1
{
my $self = shift ;
$self->day_of_week_name . ', ' .
$self->month_name . ' ' . $self->day_of_month_short . ', ' . $self->year ;
}



# eg. 14:42:49

sub time_format_1
{
my $self = shift ;
$self->hour . ':' . $self->mm . ':' . $self->second ;
}






# private methods


sub ctime
{
my $self = shift ;

my $time = time + $self->{when} ;

my 
($seconds, $minutes, $hour, $day_of_month,
 $month_number, $year_short, $nth_day_of_week, $nth_day_of_year,
 $is_daylight_savings)

 = localtime ($time) ;


($seconds, $minutes, $hour, $day_of_month,
 $month_number, $year_short, $nth_day_of_week, $nth_day_of_year,
 $is_daylight_savings) ;

} # --- end of sub ctime ---