Use the SystemReader to get system time

Change-Id: Ib79c0cc964bfe799b204419e552b9aa6243966ce

org.eclipse.jgit.test/tst/org/eclipse/jgit/util/RelativeDateFormatterTest.java

@@ -51,14 +51,22 @@ import static org.eclipse.jgit.util.RelativeDateFormatter.DAY_IN_MILLIS;
 
 import java.util.Date;
 
+import org.eclipse.jgit.junit.MockSystemReader;
 import org.eclipse.jgit.util.RelativeDateFormatter;
+import org.junit.Before;
 import org.junit.Test;
 
 public class RelativeDateFormatterTest {
 
+	@Before
+	public void setUp() {
+		SystemReader.setInstance(new MockSystemReader());
+	}
+
 	private void assertFormat(long ageFromNow, long timeUnit,
 			String expectedFormat) {
-		Date d = new Date(System.currentTimeMillis() - ageFromNow * timeUnit);
+		Date d = new Date(SystemReader.getInstance().getCurrentTime()
+				- ageFromNow * timeUnit);
 		String s = RelativeDateFormatter.format(d);
 		assertEquals(expectedFormat, s);
 	}

org.eclipse.jgit/src/org/eclipse/jgit/util/RelativeDateFormatter.java

@@ -75,7 +75,8 @@ public class RelativeDateFormatter {
 	@SuppressWarnings("boxing")
 	public static String format(Date when) {
 
-		long ageMillis = (System.currentTimeMillis() - when.getTime());
+		long ageMillis = SystemReader.getInstance().getCurrentTime()
+				- when.getTime();
 
 		// shouldn't happen in a perfect world
 		if (ageMillis < 0)