As reported in http://wordpress.org/support/topic/eo_get_add_to_google_link?replies=2, when you call eo_get_add_to_google_link() is sets the timezone of the dates returned by eo_get_the_start()/eo_get_the_end() to UTC.

DateTime objects should be cloned before altering them.