diff --git a/src/main/java/io/jsonwebtoken/Clock.java b/src/main/java/io/jsonwebtoken/Clock.java
new file mode 100644
index 00000000..7e57df80
--- /dev/null
+++ b/src/main/java/io/jsonwebtoken/Clock.java
@@ -0,0 +1,22 @@
+package io.jsonwebtoken;
+
+import io.jsonwebtoken.impl.DefaultClock;
+
+import java.util.Date;
+
+/**
+ * A clock represents a time source that can be used when creating and verifying JWTs.
+ *
+ * @since 0.7.0
+ */
+public interface Clock {
+
+    public static final Clock DEFAULT = new DefaultClock();
+
+    /**
+     * Returns the clock's current timestamp at the instant the method is invoked.
+     *
+     * @return the clock's current timestamp at the instant the method is invoked.
+     */
+    Date now();
+}
diff --git a/src/main/java/io/jsonwebtoken/JwtParser.java b/src/main/java/io/jsonwebtoken/JwtParser.java
index 11e8a5f6..e0373093 100644
--- a/src/main/java/io/jsonwebtoken/JwtParser.java
+++ b/src/main/java/io/jsonwebtoken/JwtParser.java
@@ -15,6 +15,8 @@
  */
 package io.jsonwebtoken;
 
+import io.jsonwebtoken.impl.DefaultClock;
+
 import java.security.Key;
 import java.util.Date;
 
@@ -124,6 +126,16 @@ public interface JwtParser {
      */
     JwtParser require(String claimName, Object value);
 
+    /**
+     * Sets the {@link Clock} that determines the timestamp to use when validating the parsed JWT.
+     * The parser uses a {@link DefaultClock DefaultClock} instance by default.
+     *
+     * @param clock a {@code Clock} object to return the timestamp to use when validating the parsed JWT.
+     * @return the builder instance for method chaining.
+     * @since 0.7.0
+     */
+    JwtParser setClock(Clock clock);
+
     /**
      * Sets the signing key used to verify any discovered JWS digital signature.  If the specified JWT string is not
      * a JWS (no signature), this key is not used.
diff --git a/src/main/java/io/jsonwebtoken/impl/DefaultClock.java b/src/main/java/io/jsonwebtoken/impl/DefaultClock.java
new file mode 100644
index 00000000..14d1eed7
--- /dev/null
+++ b/src/main/java/io/jsonwebtoken/impl/DefaultClock.java
@@ -0,0 +1,23 @@
+package io.jsonwebtoken.impl;
+
+import io.jsonwebtoken.Clock;
+
+import java.util.Date;
+
+/**
+ * Default {@link Clock} implementation.
+ *
+ * @since 0.7.0
+ */
+public class DefaultClock implements Clock {
+
+    /**
+     * Simply returns <code>new {@link Date}()</code>.
+     *
+     * @return a new {@link Date} instance.
+     */
+    @Override
+    public Date now() {
+        return new Date();
+    }
+}
diff --git a/src/main/java/io/jsonwebtoken/impl/DefaultJwtParser.java b/src/main/java/io/jsonwebtoken/impl/DefaultJwtParser.java
index a5d68aec..8f8c02c8 100644
--- a/src/main/java/io/jsonwebtoken/impl/DefaultJwtParser.java
+++ b/src/main/java/io/jsonwebtoken/impl/DefaultJwtParser.java
@@ -18,6 +18,7 @@ package io.jsonwebtoken.impl;
 import com.fasterxml.jackson.databind.ObjectMapper;
 import io.jsonwebtoken.ClaimJwtException;
 import io.jsonwebtoken.Claims;
+import io.jsonwebtoken.Clock;
 import io.jsonwebtoken.CompressionCodec;
 import io.jsonwebtoken.CompressionCodecResolver;
 import io.jsonwebtoken.ExpiredJwtException;
@@ -69,6 +70,8 @@ public class DefaultJwtParser implements JwtParser {
 
     Claims expectedClaims = new DefaultClaims();
 
+    private Clock clock = Clock.DEFAULT;
+
     @Override
     public JwtParser requireIssuedAt(Date issuedAt) {
         expectedClaims.setIssuedAt(issuedAt);
@@ -127,6 +130,13 @@ public class DefaultJwtParser implements JwtParser {
         return this;
     }
 
+    @Override
+    public JwtParser setClock(Clock clock) {
+        Assert.notNull(clock, "Clock instance cannot be null.");
+        this.clock = clock;
+        return this;
+    }
+
     @Override
     public JwtParser setSigningKey(byte[] key) {
         Assert.notEmpty(key, "signing key cannot be null or empty.");
@@ -346,16 +356,15 @@ public class DefaultJwtParser implements JwtParser {
         //since 0.3:
         if (claims != null) {
 
-            Date now = null;
             SimpleDateFormat sdf;
 
+            final Date now = this.clock.now();
+
             //https://tools.ietf.org/html/draft-ietf-oauth-json-web-token-30#section-4.1.4
             //token MUST NOT be accepted on or after any specified exp time:
             Date exp = claims.getExpiration();
             if (exp != null) {
 
-                now = new Date();
-
                 if (now.equals(exp) || now.after(exp)) {
                     sdf = new SimpleDateFormat(ISO_8601_FORMAT);
                     String expVal = sdf.format(exp);
@@ -371,10 +380,6 @@ public class DefaultJwtParser implements JwtParser {
             Date nbf = claims.getNotBefore();
             if (nbf != null) {
 
-                if (now == null) {
-                    now = new Date();
-                }
-
                 if (now.before(nbf)) {
                     sdf = new SimpleDateFormat(ISO_8601_FORMAT);
                     String nbfVal = sdf.format(nbf);
diff --git a/src/main/java/io/jsonwebtoken/impl/FixedClock.java b/src/main/java/io/jsonwebtoken/impl/FixedClock.java
new file mode 100644
index 00000000..88de45dc
--- /dev/null
+++ b/src/main/java/io/jsonwebtoken/impl/FixedClock.java
@@ -0,0 +1,39 @@
+package io.jsonwebtoken.impl;
+
+import io.jsonwebtoken.Clock;
+
+import java.util.Date;
+
+/**
+ * A {@code Clock} implementation that is constructed with a seed timestamp and always reports that same
+ * timestamp.
+ *
+ * @since 0.7.0
+ */
+public class FixedClock implements Clock {
+
+    private final Date now;
+
+    /**
+     * Creates a new fixed clock using <code>new {@link Date Date}()</code> as the seed timestamp.  All calls to
+     * {@link #now now()} will always return this seed Date.
+     */
+    public FixedClock() {
+        this(new Date());
+    }
+
+    /**
+     * Creates a new fixed clock using the specified seed timestamp.  All calls to
+     * {@link #now now()} will always return this seed Date.
+     *
+     * @param now the specified Date to always return from all calls to {@link #now now()}.
+     */
+    public FixedClock(Date now) {
+        this.now = now;
+    }
+
+    @Override
+    public Date now() {
+        return this.now;
+    }
+}
diff --git a/src/test/groovy/io/jsonwebtoken/JwtParserTest.groovy b/src/test/groovy/io/jsonwebtoken/JwtParserTest.groovy
index 3e37658f..40dba0c7 100644
--- a/src/test/groovy/io/jsonwebtoken/JwtParserTest.groovy
+++ b/src/test/groovy/io/jsonwebtoken/JwtParserTest.groovy
@@ -15,6 +15,8 @@
  */
 package io.jsonwebtoken
 
+import io.jsonwebtoken.impl.DefaultClock
+import io.jsonwebtoken.impl.FixedClock
 import io.jsonwebtoken.impl.TextCodec
 import org.junit.Test
 
@@ -1392,4 +1394,39 @@ class JwtParserTest {
             )
         }
     }
+
+    @Test
+    void testParseClockManipulationWithFixedClock() {
+        def then = System.currentTimeMillis() - 1000
+        Date expiry = new Date(then)
+        Date beforeExpiry = new Date(then - 1000)
+
+        String compact = Jwts.builder().setSubject('Joe').setExpiration(expiry).compact()
+
+        Jwts.parser().setClock(new FixedClock(beforeExpiry)).parse(compact)
+    }
+
+    @Test
+    void testParseClockManipulationWithNullClock() {
+        JwtParser parser = Jwts.parser();
+        try {
+            parser.setClock(null)
+            fail()
+        } catch (IllegalArgumentException expected) {
+        }
+    }
+
+    @Test
+    void testParseClockManipulationWithDefaultClock() {
+        Date expiry = new Date(System.currentTimeMillis() - 1000)
+
+        String compact = Jwts.builder().setSubject('Joe').setExpiration(expiry).compact()
+
+        try {
+            Jwts.parser().setClock(new DefaultClock()).parse(compact)
+            fail()
+        } catch (ExpiredJwtException e) {
+            assertTrue e.getMessage().startsWith('JWT expired at ')
+        }
+    }
 }
diff --git a/src/test/groovy/io/jsonwebtoken/impl/FixedClockTest.groovy b/src/test/groovy/io/jsonwebtoken/impl/FixedClockTest.groovy
new file mode 100644
index 00000000..fc092e6a
--- /dev/null
+++ b/src/test/groovy/io/jsonwebtoken/impl/FixedClockTest.groovy
@@ -0,0 +1,19 @@
+package io.jsonwebtoken.impl
+
+import org.junit.Test
+import static org.junit.Assert.*
+
+class FixedClockTest {
+
+    @Test
+    void testFixedClockDefaultConstructor() {
+
+        def clock = new FixedClock()
+
+        def date1 = clock.now()
+        Thread.sleep(100)
+        def date2 = clock.now()
+
+        assertSame date1, date2
+    }
+}