diff --git a/lib/src/main/java/com/auth0/jwt/JWTVerifier.java b/lib/src/main/java/com/auth0/jwt/JWTVerifier.java
index 07c86a4c..6cec2026 100644
--- a/lib/src/main/java/com/auth0/jwt/JWTVerifier.java
+++ b/lib/src/main/java/com/auth0/jwt/JWTVerifier.java
@@ -346,7 +346,7 @@ private boolean assertValidInstantClaim(String claimName, Claim claim, long leew
                     throw new TokenExpiredException(String.format("The Token has expired on %s.", claimVal), claimVal);
                 }
             } else {
-                isValid = assertInstantIsPast(claimVal, leeway, now);
+                isValid = assertInstantIsLessThanOrEqualToNow(claimVal, leeway, now);
                 if (!isValid) {
                     throw new IncorrectClaimException(
                             String.format("The Token can't be used before %s.", claimVal), claimName, claim);
@@ -356,10 +356,10 @@ private boolean assertValidInstantClaim(String claimName, Claim claim, long leew
         }
 
         private boolean assertInstantIsFuture(Instant claimVal, long leeway, Instant now) {
-            return !(claimVal != null && now.minus(Duration.ofSeconds(leeway)).isAfter(claimVal));
+            return claimVal == null || now.minus(Duration.ofSeconds(leeway)).isBefore(claimVal);
         }
 
-        private boolean assertInstantIsPast(Instant claimVal, long leeway, Instant now) {
+        private boolean assertInstantIsLessThanOrEqualToNow(Instant claimVal, long leeway, Instant now) {
             return !(claimVal != null && now.plus(Duration.ofSeconds(leeway)).isBefore(claimVal));
         }
 
diff --git a/lib/src/test/java/com/auth0/jwt/JWTTest.java b/lib/src/test/java/com/auth0/jwt/JWTTest.java
index b9f56a2e..087f1e9e 100644
--- a/lib/src/test/java/com/auth0/jwt/JWTTest.java
+++ b/lib/src/test/java/com/auth0/jwt/JWTTest.java
@@ -12,6 +12,7 @@
 import java.security.interfaces.ECKey;
 import java.security.interfaces.RSAKey;
 import java.time.Clock;
+import java.time.Duration;
 import java.time.Instant;
 import java.time.ZoneId;
 import java.util.Base64;
@@ -270,12 +271,12 @@ public void shouldGetStringAudience() {
     @Test
     public void shouldGetExpirationTime() {
         long seconds = 1477592L;
-        Clock clock = Clock.fixed(Instant.ofEpochSecond(seconds), ZoneId.of("UTC"));
+        Clock mockNow = Clock.fixed(Instant.ofEpochSecond(seconds - 1), ZoneId.of("UTC"));
 
         String token = "eyJhbGciOiJIUzI1NiJ9.eyJleHAiOjE0Nzc1OTJ9.x_ZjkPkKYUV5tdvc0l8go6D_z2kez1MQcOxokXrDc3k";
         JWTVerifier.BaseVerification verification = (JWTVerifier.BaseVerification) JWT.require(Algorithm.HMAC256("secret"));
         DecodedJWT jwt = verification
-                .build(clock)
+                .build(mockNow)
                 .verify(token);
 
         assertThat(jwt, is(notNullValue()));
diff --git a/lib/src/test/java/com/auth0/jwt/JWTVerifierTest.java b/lib/src/test/java/com/auth0/jwt/JWTVerifierTest.java
index 6d8ba201..5a784b87 100644
--- a/lib/src/test/java/com/auth0/jwt/JWTVerifierTest.java
+++ b/lib/src/test/java/com/auth0/jwt/JWTVerifierTest.java
@@ -657,6 +657,7 @@ public void shouldThrowOnNegativeCustomLeeway() {
     }
 
     // Expires At
+
     @Test
     public void shouldValidateExpiresAtWithLeeway() {
         String token = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJleHAiOjE0Nzc1OTJ9.isvT0Pqx0yjnZk53mUFSeYFJLDs-Ls9IsNAm86gIdZo";
@@ -674,12 +675,26 @@ public void shouldValidateExpiresAtIfPresent() {
         String token = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJleHAiOjE0Nzc1OTJ9.isvT0Pqx0yjnZk53mUFSeYFJLDs-Ls9IsNAm86gIdZo";
         JWTVerifier.BaseVerification verification = (JWTVerifier.BaseVerification) JWTVerifier.init(Algorithm.HMAC256("secret"));
         DecodedJWT jwt = verification
-                .build(mockNow)
+                .build(mockOneSecondEarlier)
                 .verify(token);
 
         assertThat(jwt, is(notNullValue()));
     }
 
+    @Test
+    public void shouldThrowWhenExpiresAtIsNow() {
+        // exp must be > now
+        TokenExpiredException e = assertThrows(null, TokenExpiredException.class, () -> {
+            String token = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJleHAiOjE0Nzc1OTJ9.isvT0Pqx0yjnZk53mUFSeYFJLDs-Ls9IsNAm86gIdZo";
+            JWTVerifier.BaseVerification verification = (JWTVerifier.BaseVerification) JWTVerifier.init(Algorithm.HMAC256("secret"));
+            verification
+                    .build(mockNow)
+                    .verify(token);
+        });
+        assertThat(e.getMessage(), is("The Token has expired on 1970-01-18T02:26:32Z."));
+        assertThat(e.getExpiredOn(), is(Instant.ofEpochSecond(1477592L)));
+    }
+
     @Test
     public void shouldThrowOnInvalidExpiresAtIfPresent() {
         TokenExpiredException e = assertThrows(null, TokenExpiredException.class, () -> {
@@ -731,7 +746,18 @@ public void shouldThrowOnInvalidNotBeforeIfPresent() {
 
     @Test
     public void shouldValidateNotBeforeIfPresent() {
-        String token = "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJleHAiOjE0Nzc1OTJ9.isvT0Pqx0yjnZk53mUFSeYFJLDs-Ls9IsNAm86gIdZo";
+        String token = "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJuYmYiOjE0Nzc1OTN9.f4zVV0TbbTG5xxDjSoGZ320JIMchGoQCWrnT5MyQdT0";
+        JWTVerifier.BaseVerification verification = (JWTVerifier.BaseVerification) JWTVerifier.init(Algorithm.HMAC256("secret"));
+        DecodedJWT jwt = verification
+                .build(mockOneSecondLater)
+                .verify(token);
+
+        assertThat(jwt, is(notNullValue()));
+    }
+
+    @Test
+    public void shouldAcceptNotBeforeEqualToNow() {
+        String token = "eyJ0eXAiOiJKV1QiLCJhbGciOiJIUzI1NiJ9.eyJuYmYiOjE0Nzc1OTJ9.71XBtRmkAa4iKnyhbS4NPW-Xr26eAVAdHZgmupS7a5o";
         JWTVerifier.BaseVerification verification = (JWTVerifier.BaseVerification) JWTVerifier.init(Algorithm.HMAC256("secret"));
         DecodedJWT jwt = verification
                 .build(mockNow)