I have just done a fresh install of V2.3.4 on a new host server.

When I uploaded my first image the following error message began to appear on various admin pages.

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Warning: mktime() [function.mktime]: 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 'America/Chicago' for 'CDT/-5.0/DST' instead in /home2/webi8726/public_html/lumix/gallery/demo23/include/functions.inc.php on line 520
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AND
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Warning: strftime() [function.strftime]: 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 'America/Chicago' for 'CDT/-5.0/DST' instead in /home2/webi8726/public_html/lumix/gallery/demo23/include/smarty/libs/Smarty_Compiler.class.php on line 400
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How can I resolve this?