References
Reference NO 1
http://stackoverflow.com/questions/15165438/why-is-a-symbol-required-for-some-datetime-objects-in-php
Reference NO 2
http://php.net/manual/en/datetime.createfromformat.php
Reference NO 3
http://blog.lysender.com/2012/11/php-setting-and-getting-timestamp-from-datetime-object-below-php-5-3-x/
Reference NO 4
https://sheriframadan.com/2012/12/php-oop-objects-under-the-hood/
Reference NO 5
http://www.codebyjeff.com/blog/2013/03/datetime-magic-in-php
Reference NO 6
http://www.phptherightway.com/
Reference NO 7
http://www.w3schools.com/php/func_date_create_from_format.asp?output=print
Reference NO 8
http://wiki.quantsoftware.org/index.php?title=QSTK_Tutorial_4