diff --git a/src/main/java/org/kohsuke/github/GitHub.java b/src/main/java/org/kohsuke/github/GitHub.java
index 9fbcac916..0cbf42597 100644
--- a/src/main/java/org/kohsuke/github/GitHub.java
+++ b/src/main/java/org/kohsuke/github/GitHub.java
@@ -956,7 +956,9 @@ public class GitHub {
     }
 
     /*package*/ static String printDate(Date dt) {
-        return new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'").format(dt);
+        SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'");
+        df.setTimeZone(TimeZone.getTimeZone("GMT"));
+        return df.format(dt);
     }
 
     /*package*/ static final ObjectMapper MAPPER = new ObjectMapper();
diff --git a/src/test/java/org/kohsuke/github/GHMilestoneTest.java b/src/test/java/org/kohsuke/github/GHMilestoneTest.java
index f987fd669..028dba684 100644
--- a/src/test/java/org/kohsuke/github/GHMilestoneTest.java
+++ b/src/test/java/org/kohsuke/github/GHMilestoneTest.java
@@ -21,7 +21,7 @@ public class GHMilestoneTest extends AbstractGitHubWireMockTest {
             return;
         }
 
-        for (GHMilestone milestone : getRepository().listMilestones(GHIssueState.ALL)) {
+        for (GHMilestone milestone : getRepository(gitHubBeforeAfter).listMilestones(GHIssueState.ALL)) {
             if ("Original Title".equals(milestone.getTitle()) ||
                 "Updated Title".equals(milestone.getTitle())) {
                 milestone.delete();
@@ -37,7 +37,8 @@ public class GHMilestoneTest extends AbstractGitHubWireMockTest {
 
         String NEW_TITLE = "Updated Title";
         String NEW_DESCRIPTION = "Updated Description";
-        Date NEW_DUE_DATE = GitHub.parseDate("2020-10-01T17:00:00Z");
+        Date NEW_DUE_DATE = GitHub.parseDate("2020-10-01T13:00:00Z");
+        Date OUTPUT_DUE_DATE = GitHub.parseDate("2020-10-01T13:00:00Z");
 
         milestone.setTitle(NEW_TITLE);
         milestone.setDescription(NEW_DESCRIPTION);
@@ -48,8 +49,7 @@ public class GHMilestoneTest extends AbstractGitHubWireMockTest {
 
         assertEquals(NEW_TITLE, milestone.getTitle());
         assertEquals(NEW_DESCRIPTION, milestone.getDescription());
-        // The dates never seem to match exactly...
-        //assertEquals(NEW_DUE_DATE, milestone.getDueOn());
+        assertEquals(NEW_DUE_DATE, milestone.getDueOn());
         assertNotNull(milestone.getDueOn());
     }
 
diff --git a/src/test/java/org/kohsuke/github/GitHubStaticTest.java b/src/test/java/org/kohsuke/github/GitHubStaticTest.java
new file mode 100644
index 000000000..793f23cc7
--- /dev/null
+++ b/src/test/java/org/kohsuke/github/GitHubStaticTest.java
@@ -0,0 +1,72 @@
+package org.kohsuke.github;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+import java.text.SimpleDateFormat;
+import java.time.Instant;
+import java.time.temporal.ChronoUnit;
+import java.util.Date;
+import java.util.TimeZone;
+
+import static org.hamcrest.CoreMatchers.equalTo;
+import static org.hamcrest.CoreMatchers.not;
+
+/**
+ * Unit test for {@link GitHub} static helpers.
+ *
+ * @author Liam Newman
+ */
+public class GitHubStaticTest extends Assert {
+
+    @Test
+    public void timeRoundTrip() throws Exception {
+        Instant instantNow = Instant.now();
+
+        Date instantSeconds = Date.from(instantNow.truncatedTo(ChronoUnit.SECONDS));
+        Date instantMillis = Date.from(instantNow.truncatedTo(ChronoUnit.MILLIS));
+
+        // TODO: other formats
+        String instantFormatSlash = formatDate(instantMillis, "yyyy/MM/dd HH:mm:ss ZZZZ");
+        String instantFormatDash = formatDate(instantMillis, "yyyy-MM-dd'T'HH:mm:ss'Z'");
+        String instantFormatMillis = formatDate(instantMillis, "yyyy-MM-dd'T'HH:mm:ss.S'Z'");
+        String instantSecondsFormatMillis = formatDate(instantSeconds, "yyyy-MM-dd'T'HH:mm:ss.S'Z'");
+        String instantBadFormat = formatDate(instantMillis, "yy-MM-dd'T'HH:mm'Z'");
+
+
+        assertThat(GitHub.parseDate(GitHub.printDate(instantSeconds)),
+            equalTo(GitHub.parseDate(GitHub.printDate(instantMillis))));
+
+        assertThat(instantSeconds,
+            equalTo(GitHub.parseDate(GitHub.printDate(instantSeconds))));
+
+        assertThat(instantMillis,
+            not(equalTo(GitHub.parseDate(GitHub.printDate(instantMillis)))));
+
+        assertThat(instantSeconds,
+            equalTo(GitHub.parseDate(instantFormatSlash)));
+
+        assertThat(instantSeconds,
+            equalTo(GitHub.parseDate(instantFormatDash)));
+
+        assertThat(instantMillis,
+            equalTo(GitHub.parseDate(instantFormatMillis)));
+
+        assertThat(instantSeconds,
+            equalTo(GitHub.parseDate(instantSecondsFormatMillis)));
+
+        try {
+            GitHub.parseDate(instantBadFormat);
+            fail("Bad time format should throw.");
+        } catch (IllegalStateException e) {
+            assertThat(e.getMessage(), equalTo("Unable to parse the timestamp: " + instantBadFormat));
+        }
+    }
+
+    static String formatDate(Date dt, String format) {
+        SimpleDateFormat df = new SimpleDateFormat(format);
+        df.setTimeZone(TimeZone.getTimeZone("GMT"));
+        return df.format(dt);
+    }
+
+}