Date issue

I have posted a code last week about that date format problem, well I have figured out a much lesser coding.

#!/usr/bin/bash
clear
export NLS_LANG=AMERICAN_AMERICA.AL32UTF8



if [ $# -lt 2 ]  ; then
        echo " Incorrect Number of Arguments";
        echo " Usage : Main_Script <FROM_DATE> <TO_DATE>";
        echo " Example : Main_Script 21-JUL-2015 30-JUL-2015";
        exit;

fi;

if [ $# == 2 ]; then
      if [[ $1 == [0-3][0-9]-[A-Z][A-Z][A-Z]-[0-9][0-9][0-9][0-9] ]]; then
              if  [[ $2 == [0-3][0-9]-[A-Z][A-Z][A-Z]-[0-9][0-9][0-9][0-9] ]];
                  then
                  d1=`date -d $1 +%s`
                  d2=`date -d $2 +%s`
                echo $d1;
                echo $d2;

                                        if [[ $d2 -gt $d1 ]];
                                        then
                                        echo "correct";

                      else
                                                 echo "Start date is more than end date";

                         exit;

 fi;
                   else
                   echo "Incorrect date format";
                   echo  $2;
                                  echo "Usage : DD-MMM-YYYY";
                  echo " Example :  Main_Script 21-JUL-2015 30-JUL-2015";
                  exit;
       fi;
           else
            echo "Incorrect date format";
                echo  $1;
                 echo "Usage : DD-MMM-YYYY";
                echo " Example :  Main_Script 21-JUL-2015 30-JUL-2015";
                exit;


    fi;
fi;

Sample Input : sh date.sh 01-JAN-2015 01-DEC-2014
Sample Output : 1420050600
1417372200
Start date is more than end date

This above stuff is for Linux environment, but when I'm trying to do the same in Solaris it is showing an error as "date -d : illegal format".
Can you help me adjusting some part of this code so that it can run on Solaris as well so that I dont have to install GNU utility package.

There is already a similar post of yours, with several comments and suggestions. Please only have one thread per question.
Feel free to continue the discussion in your original thread.