New Error Message: Uncaught exception 'Exception' with message 'DateTime::__construct()

[NobodysHero]

There's this one:

[16-Oct-2016 15:20:42 UTC] PHP Fatal error: Uncaught exception 'Exception' with message 'DateTime::__construct(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of those methods and you are still getting this warning, you most likely misspelled the timezone identifier. We selected the timezone 'UTC' for now, but please set date.timezone to select your timezone.' in /home/mystfell/public_html/classes/class_member.php:36
Stack trace:
#0 /home/mystfell/public_html/classes/class_member.php(36): DateTime->__construct()
#1 /home/mystfell/public_html/classes/class_admin.php(16): Member->__construct('1')
#2 /home/mystfell/public_html/classes/class_membercreator.php(54): Admin->__construct('1')
#3 /home/mystfell/public_html/classes/class_membercreator.php(35): MemberCreator->create_admin()
#4 /home/mystfell/public_html/classes/class_mysidia.php(273): MemberCreator->create()
#5 /home/mystfell/public_html/classes/class_mysidia.php(168): in /home/mystfell/public_html/classes/class_member.php on line 36

And this one:

[16-Oct-2016 15:21:38 UTC] PHP Fatal error: Uncaught exception 'Exception' with message 'DateTime::__construct(): It is not safe to rely on the system's timezone settings. You are *required* to use the date.timezone setting or the date_default_timezone_set() function. In case you used any of those methods and you are still getting this warning, you most likely misspelled the timezone identifier. We selected the timezone 'UTC' for now, but please set date.timezone to select your timezone.' in /home/mystfell/public_html/classes/class_visitor.php:14
Stack trace:
#0 /home/mystfell/public_html/classes/class_visitor.php(14): DateTime->__construct()
#1 /home/mystfell/public_html/classes/class_visitorcreator.php(34): Visitor->__construct('173.254.250.226')
#2 /home/mystfell/public_html/classes/class_visitorcreator.php(20): VisitorCreator->create_guest()
#3 /home/mystfell/public_html/classes/class_mysidia.php(273): VisitorCreator->create()
#4 /home/mystfell/public_html/classes/class_mysidia.php(168): Mysidia->getCurrentUser()
#5 /home/mystfell/public_html/class in /home/mystfell/public_html/classes/class_visitor.php on line 14

Please help. T_T