is_leap_year ()  
{

declare -i year=$1      

echo -n "$year ($2)-> " 

if (( $year % 4 == 0 )) 
then
        if (( $year % 400 == 0 ))       
        then
                echo "This is a leap year"
        else
                if (( $year % 100 == 0 )) 
                then
                        echo "This is not a leap year"
                else
                        echo "This is a leap year" 
                fi
        fi
else
        echo "This is not a leap year"
fi


}



is_leap_year 1900 not 
is_leap_year 2000 is  
is_leap_year 2001 not 
is_leap_year 2003 not 
is_leap_year 2004 is