diff --git a/tests/Unit/framework/ConfigTest.php b/tests/Unit/framework/ConfigTest.php
new file mode 100644
index 000000000..b9ef136d2
--- /dev/null
+++ b/tests/Unit/framework/ConfigTest.php
@@ -0,0 +1,26 @@
+<?php
+
+class ConfigTest extends \Codeception\TestCase\Test
+{
+	public function testConfig()
+	{
+		if (!file_exists(RX_BASEDIR . 'files/config/config.php'))
+		{
+			mkdir(RX_BASEDIR . 'files/config', 0755, true);
+			copy(RX_BASEDIR . 'common/defaults/config.php', RX_BASEDIR . 'files/config/config.php');
+		}
+		
+		Rhymix\Framework\Config::init();
+		$this->assertTrue(version_compare(Rhymix\Framework\Config::get('config_version'), '2.0', '>='));
+		$this->assertTrue(is_array(Rhymix\Framework\Config::get('db.master')));
+		$this->assertNotEmpty(Rhymix\Framework\Config::get('db.master.host'));
+		
+		Rhymix\Framework\Config::set('foo.bar', $rand = mt_rand());
+		$this->assertEquals(array('bar' => $rand), Rhymix\Framework\Config::get('foo'));
+		$this->assertEquals($rand, Rhymix\Framework\Config::get('foo.bar'));
+		
+		$var = array('foo' => 'bar');
+		$serialized = "array(\n\t'foo' => 'bar',\n)";
+		$this->assertEquals($serialized, Rhymix\Framework\Config::serialize($var));
+	}
+}
diff --git a/tests/Unit/framework/DateTimeTest.php b/tests/Unit/framework/DateTimeTest.php
new file mode 100644
index 000000000..e25f0e424
--- /dev/null
+++ b/tests/Unit/framework/DateTimeTest.php
@@ -0,0 +1,135 @@
+<?php
+
+class DateTimeTest extends \Codeception\TestCase\Test
+{
+	public function _before()
+	{
+		// Add some dummy data to system configuration. Asia/Seoul offset is 32400.
+		Rhymix\Framework\Config::set('locale.default_timezone', 'Asia/Seoul');
+		Rhymix\Framework\Config::set('locale.internal_timezone', 10800);
+		
+		// Set PHP time zone to the internal time zone.
+		$old_timezone = @date_default_timezone_get();
+		date_default_timezone_set('Etc/GMT-3');
+	}
+	
+	public function _after()
+	{
+		// Restore the old timezone.
+		date_default_timezone_set($old_timezone);
+	}
+	
+	public function testZgap()
+	{
+		// Test zgap() when the current user's time zone is different from the system default.
+		$_SESSION['timezone'] = 'Etc/UTC';
+		$this->assertEquals(-10800, zgap());
+		
+		// Test zgap() when the current user's time zone is the same as the system default.
+		unset($_SESSION['timezone']);
+		$this->assertEquals(21600, zgap());
+	}
+	
+	public function testZtime()
+	{
+		$timestamp = 1454000000;
+		
+		// Test ztime() when the internal time zone is different from the default time zone.
+		Rhymix\Framework\Config::set('locale.internal_timezone', 10800);
+		$this->assertEquals($timestamp, ztime('20160128195320'));
+		
+		// Test ztime() when the internal time zone is the same as the default time zone.
+		Rhymix\Framework\Config::set('locale.internal_timezone', 32400);
+		$this->assertEquals($timestamp, ztime('20160129015320'));
+		
+		// Restore the internal timezone.
+		Rhymix\Framework\Config::set('locale.internal_timezone', 10800);
+	}
+	
+	public function testZdate()
+	{
+		$expected = '2016-01-29 01:53:20';
+		
+		// Test zdate() when the internal time zone is different from the default time zone.
+		Rhymix\Framework\Config::set('locale.internal_timezone', 10800);
+		$this->assertEquals($expected, zdate('20160128195320'));
+		
+		// Test zdate() when the internal time zone is the same as the default time zone.
+		Rhymix\Framework\Config::set('locale.internal_timezone', 32400);
+		$this->assertEquals($expected, zdate('20160129015320'));
+		
+		// Restore the internal timezone.
+		Rhymix\Framework\Config::set('locale.internal_timezone', 10800);
+	}
+	
+	public function testGetTimezoneForCurrentUser()
+	{
+		// Test when the current user's time zone is different from the system default.
+		$_SESSION['timezone'] = 'Pacific/Auckland';
+		$this->assertEquals('Pacific/Auckland', Rhymix\Framework\DateTime::getTimezoneForCurrentUser());
+		
+		// Test when the current user's time zone is the same as the system default.
+		unset($_SESSION['timezone']);
+		$this->assertEquals('Asia/Seoul', Rhymix\Framework\DateTime::getTimezoneForCurrentUser());
+	}
+	
+	public function testFormatTimestampForCurrentUser()
+	{
+		$timestamp_winter = 1454000000;
+		$timestamp_summer = $timestamp_winter - (86400 * 184);
+		
+		// Test when the current user's time zone is in the Northern hemisphere with DST.
+		$_SESSION['timezone'] = 'America/Chicago';
+		$this->assertEquals('20160128 105320', Rhymix\Framework\DateTime::formatTimestampForCurrentUser('Ymd His', $timestamp_winter));
+		$this->assertEquals('20150728 115320', Rhymix\Framework\DateTime::formatTimestampForCurrentUser('Ymd His', $timestamp_summer));
+		
+		// Test when the current user's time zone is in the Southern hemisphere with DST.
+		$_SESSION['timezone'] = 'Pacific/Auckland';
+		$this->assertEquals('20160129 055320', Rhymix\Framework\DateTime::formatTimestampForCurrentUser('Ymd His', $timestamp_winter));
+		$this->assertEquals('20150729 045320', Rhymix\Framework\DateTime::formatTimestampForCurrentUser('Ymd His', $timestamp_summer));
+		
+		// Test when the current user's time zone is the same as the system default without DST.
+		unset($_SESSION['timezone']);
+		$this->assertEquals('20160129 015320', Rhymix\Framework\DateTime::formatTimestampForCurrentUser('Ymd His', $timestamp_winter));
+		$this->assertEquals('20150729 015320', Rhymix\Framework\DateTime::formatTimestampForCurrentUser('Ymd His', $timestamp_summer));
+	}
+	
+	public function testGetTimezoneList()
+	{
+		$tzlist = Rhymix\Framework\DateTime::getTimezoneList();
+		$this->assertTrue(array_key_exists('Etc/UTC', $tzlist));
+		$this->assertEquals('Asia/Seoul (+09:00)', $tzlist['Asia/Seoul']);
+	}
+	
+	public function testGetTimezoneOffset()
+	{
+		$this->assertEquals(32400, Rhymix\Framework\DateTime::getTimezoneOffset('Asia/Seoul'));
+		$this->assertEquals(39600, Rhymix\Framework\DateTime::getTimezoneOffset('Australia/Sydney', strtotime('2016-01-01')));
+		$this->assertEquals(36000, Rhymix\Framework\DateTime::getTimezoneOffset('Australia/Sydney', strtotime('2015-07-01')));
+		$this->assertEquals(-18000, Rhymix\Framework\DateTime::getTimezoneOffset('America/New_York', strtotime('2016-01-01')));
+		$this->assertEquals(-14400, Rhymix\Framework\DateTime::getTimezoneOffset('America/New_York', strtotime('2015-07-01')));
+	}
+	
+	public function testGetTimezoneOffsetFromInternal()
+	{
+		$this->assertEquals(21600, Rhymix\Framework\DateTime::getTimezoneOffsetFromInternal('Asia/Seoul'));
+		$this->assertEquals(28800, Rhymix\Framework\DateTime::getTimezoneOffsetFromInternal('Australia/Sydney', strtotime('2016-01-01')));
+		$this->assertEquals(25200, Rhymix\Framework\DateTime::getTimezoneOffsetFromInternal('Australia/Sydney', strtotime('2015-07-01')));
+		$this->assertEquals(-28800, Rhymix\Framework\DateTime::getTimezoneOffsetFromInternal('America/New_York', strtotime('2016-01-01')));
+		$this->assertEquals(-25200, Rhymix\Framework\DateTime::getTimezoneOffsetFromInternal('America/New_York', strtotime('2015-07-01')));
+	}
+	
+	public function testGetTimezoneOffsetByLegacyFormat()
+	{
+		$this->assertEquals(32400, Rhymix\Framework\DateTime::getTimezoneOffsetByLegacyFormat('+0900'));
+		$this->assertEquals(-25200, Rhymix\Framework\DateTime::getTimezoneOffsetByLegacyFormat('-0700'));
+		$this->assertEquals(19800, Rhymix\Framework\DateTime::getTimezoneOffsetByLegacyFormat('+0530'));
+		$this->assertEquals(-38700, Rhymix\Framework\DateTime::getTimezoneOffsetByLegacyFormat('-1045'));
+	}
+	
+	public function testGetTimezoneNameByOffset()
+	{
+		$this->assertEquals('Etc/GMT-9', Rhymix\Framework\DateTime::getTimezoneNameByOffset(32400));
+		$this->assertEquals('Etc/GMT+5', Rhymix\Framework\DateTime::getTimezoneNameByOffset(-18000));
+	}
+}