diff --git a/dhp-common/pom.xml b/dhp-common/pom.xml
index acac3594f..b1494f649 100644
--- a/dhp-common/pom.xml
+++ b/dhp-common/pom.xml
@@ -21,6 +21,10 @@
 			<groupId>org.apache.hadoop</groupId>
 			<artifactId>hadoop-common</artifactId>
 		</dependency>
+		<dependency>
+			<groupId>commons-validator</groupId>
+			<artifactId>commons-validator</artifactId>
+		</dependency>
 		<dependency>
 			<groupId>org.apache.spark</groupId>
 			<artifactId>spark-core_2.11</artifactId>
diff --git a/dhp-common/src/main/java/eu/dnetlib/dhp/schema/oaf/utils/GraphCleaningFunctions.java b/dhp-common/src/main/java/eu/dnetlib/dhp/schema/oaf/utils/GraphCleaningFunctions.java
index 15fff07c0..da253c681 100644
--- a/dhp-common/src/main/java/eu/dnetlib/dhp/schema/oaf/utils/GraphCleaningFunctions.java
+++ b/dhp-common/src/main/java/eu/dnetlib/dhp/schema/oaf/utils/GraphCleaningFunctions.java
@@ -7,11 +7,13 @@ import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
 import org.apache.commons.lang3.StringUtils;
+import org.apache.commons.validator.GenericValidator;
 
 import com.google.common.collect.Lists;
 import com.google.common.collect.Sets;
 
 import eu.dnetlib.dhp.schema.common.ModelConstants;
+import eu.dnetlib.dhp.schema.common.ModelSupport;
 import eu.dnetlib.dhp.schema.oaf.*;
 
 public class GraphCleaningFunctions extends CleaningFunctions {
@@ -115,7 +117,13 @@ public class GraphCleaningFunctions extends CleaningFunctions {
 				o.setCountry(ModelConstants.UNKNOWN_COUNTRY);
 			}
 		} else if (value instanceof Relation) {
-			// nothing to clean here
+			Relation r = (Relation) value;
+
+			if (!isValidDate(r.getValidationDate())) {
+				r.setValidationDate(null);
+				r.setValidated(false);
+			}
+
 		} else if (value instanceof Result) {
 
 			Result r = (Result) value;
@@ -292,6 +300,12 @@ public class GraphCleaningFunctions extends CleaningFunctions {
 		return value;
 	}
 
+	protected static boolean isValidDate(String date) {
+		return Stream
+			.of(ModelSupport.DATE_TIME_FORMATS)
+			.anyMatch(format -> GenericValidator.isDate(date, format, false));
+	}
+
 	// HELPERS
 
 	private static boolean isValidAuthorName(Author a) {
diff --git a/dhp-common/src/test/java/eu/dnetlib/dhp/schema/oaf/utils/OafMapperUtilsTest.java b/dhp-common/src/test/java/eu/dnetlib/dhp/schema/oaf/utils/OafMapperUtilsTest.java
index 7256d6489..e8135f201 100644
--- a/dhp-common/src/test/java/eu/dnetlib/dhp/schema/oaf/utils/OafMapperUtilsTest.java
+++ b/dhp-common/src/test/java/eu/dnetlib/dhp/schema/oaf/utils/OafMapperUtilsTest.java
@@ -4,6 +4,7 @@ package eu.dnetlib.dhp.schema.oaf.utils;
 import static org.junit.jupiter.api.Assertions.*;
 
 import java.io.IOException;
+import java.time.format.DateTimeParseException;
 import java.util.HashSet;
 import java.util.List;
 import java.util.stream.Collectors;
@@ -15,16 +16,23 @@ import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.ObjectMapper;
 
 import eu.dnetlib.dhp.schema.common.ModelConstants;
-import eu.dnetlib.dhp.schema.oaf.Dataset;
-import eu.dnetlib.dhp.schema.oaf.KeyValue;
-import eu.dnetlib.dhp.schema.oaf.Publication;
-import eu.dnetlib.dhp.schema.oaf.Result;
+import eu.dnetlib.dhp.schema.oaf.*;
 
 public class OafMapperUtilsTest {
 
 	private static final ObjectMapper OBJECT_MAPPER = new ObjectMapper()
 		.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
 
+	@Test
+	public void testDateValidation() {
+
+		assertTrue(GraphCleaningFunctions.isValidDate("2016-05-07T12:41:19.202Z"));
+		assertTrue(GraphCleaningFunctions.isValidDate("2020-09-10 11:08:52"));
+		assertTrue(GraphCleaningFunctions.isValidDate("2016-04-05"));
+		assertFalse(GraphCleaningFunctions.isValidDate("2016 April 05"));
+
+	}
+
 	@Test
 	public void testMergePubs() throws IOException {
 		Publication p1 = read("publication_1.json", Publication.class);
diff --git a/pom.xml b/pom.xml
index 5e5fec308..5b96816d9 100644
--- a/pom.xml
+++ b/pom.xml
@@ -200,6 +200,12 @@
 				<version>${dhp.commons.lang.version}</version>
 			</dependency>
 
+            <dependency>
+                <groupId>commons-validator</groupId>
+                <artifactId>commons-validator</artifactId>
+                <version>1.7</version>
+            </dependency>
+
 			<dependency>
 				<groupId>com.google.guava</groupId>
 				<artifactId>guava</artifactId>
@@ -730,7 +736,7 @@
 		<mockito-core.version>3.3.3</mockito-core.version>
 		<mongodb.driver.version>3.4.2</mongodb.driver.version>
 		<vtd.version>[2.12,3.0)</vtd.version>
-		<dhp-schemas.version>[2.5.10]</dhp-schemas.version>
+		<dhp-schemas.version>[2.5.11]</dhp-schemas.version>
 		<dnet-actionmanager-api.version>[4.0.3]</dnet-actionmanager-api.version>
 		<dnet-actionmanager-common.version>[6.0.5]</dnet-actionmanager-common.version>
 		<dnet-openaire-broker-common.version>[3.1.6]</dnet-openaire-broker-common.version>