BUGFIX: Correct testSetNullAndZeroValues() of DatetimeTest

- Code was assuming NZ time zone
- Set the default timezone to UTC for the test
- Correct the expected times for the epoch from noon to 00:00:00 UTC

tests/model/DatetimeTest.php

@@ -35,6 +35,8 @@ function testNowWithMockDate() {
 	}
 
 	function testSetNullAndZeroValues() {
+		date_default_timezone_set('UTC');
+
 		$date = DBField::create('SS_Datetime', '');
 		$this->assertNull($date->getValue(), 'Empty string evaluates to NULL');
 
@@ -45,10 +47,10 @@ function testSetNullAndZeroValues() {
 		$this->assertNull($date->getValue(), 'Boolean FALSE evaluates to NULL');
 
 		$date = DBField::create('SS_Datetime', '0');
-		$this->assertEquals('1970-01-01 12:00:00', $date->getValue(), 'String zero is UNIX epoch time');
+		$this->assertEquals('1970-01-01 00:00:00', $date->getValue(), 'String zero is UNIX epoch time');
 
 		$date = DBField::create('SS_Datetime', 0);
-		$this->assertEquals('1970-01-01 12:00:00', $date->getValue(), 'Numeric zero is UNIX epoch time');
+		$this->assertEquals('1970-01-01 00:00:00', $date->getValue(), 'Numeric zero is UNIX epoch time');
 	}
 
 }