There are two things that might cause this. The first is in OST itself, the second is in PHP.
For the OST one log in as an admin.
Click on "Admin Panel".
click on "Settings".
Scroll down the section entitled "Date & Time".
Under "Default Timezone:" make sure that you have selected GMT -5.0 (Eastern Time (US & Canada), Bogota, Lima)
note: alternatively selecting server time here might be ok
Secondly, You should tell php what timezine you are located in by adding the following to your php.ini:
date.timezone = "America/New_York"
note: I think that you can use "US/Eastern" also.
More information on this can be found at: http://www.php.net/manual/en/timezones.php(http://www.php.net/manual/en/timezones.php)
