delegating the date parsing to https://github.com/sisyphsu/dateparser

pom.xml

@@ -262,6 +262,12 @@
                 <version>${dhp.commons.lang.version}</version>
             </dependency>
 
+            <dependency>
+                <groupId>com.github.sisyphsu</groupId>
+                <artifactId>dateparser</artifactId>
+                <version>1.0.7</version>
+            </dependency>
+
             <dependency>
                 <groupId>com.google.guava</groupId>
                 <artifactId>guava</artifactId>
@@ -330,6 +336,11 @@
             <artifactId>commons-lang3</artifactId>
         </dependency>
 
+        <dependency>
+            <groupId>com.github.sisyphsu</groupId>
+            <artifactId>dateparser</artifactId>
+        </dependency>
+
         <dependency>
             <groupId>com.fasterxml.jackson.core</groupId>
             <artifactId>jackson-databind</artifactId>

src/main/java/eu/dnetlib/dhp/schema/common/ModelSupport.java

@@ -15,6 +15,7 @@ import org.apache.commons.codec.binary.Hex;
 import org.apache.commons.lang3.StringUtils;
 import org.apache.commons.lang3.time.DateUtils;
 
+import com.github.sisyphsu.dateparser.DateParserUtils;
 import com.google.common.collect.Maps;
 
 import eu.dnetlib.dhp.schema.oaf.*;
@@ -305,13 +306,7 @@ public class ModelSupport {
 
 	private static final String schemeTemplate = "dnet:%s_%s_relations";
 
-	public static final String[] DATE_TIME_FORMATS = {
-			"yyyy-MM-dd'T'hh:mm:ss.SSS'Z'",
-			"yyyy-MM-dd'T'hh:mm:ss'Z'",
-			"yyyy-MM-dd hh:mm:ss'Z'",
-			"yyyy-MM-dd hh:mm:ss",
-			"yyyy-MM-dd"
-	};
+	public static final String DATE_FORMAT = "yyyy-MM-dd";
 
 	private ModelSupport() {
 	}
@@ -506,8 +501,8 @@ public class ModelSupport {
 		}
 		if (StringUtils.isNotBlank(dateA) && StringUtils.isNotBlank(dateB)) {
 
-			final Date a = tryParse(dateA);
-			final Date b = tryParse(dateB);
+			final Date a = DateParserUtils.parseDate(dateA);
+			final Date b = DateParserUtils.parseDate(dateB);
 
 			if (Objects.nonNull(a) && Objects.nonNull(b)) {
 				return a.before(b) ? dateA : dateB;
@@ -519,14 +514,4 @@ public class ModelSupport {
 		}
 	}
 
-	private static Date tryParse(String date) throws DateTimeParseException {
-		try {
-			return DateUtils.parseDate(date, DATE_TIME_FORMATS);
-		} catch (ParseException e) {
-			// ignore it, try another format
-		}
-		final String formats = String.join("\n", Arrays.asList(DATE_TIME_FORMATS));
-		throw new DateTimeParseException(String.format("cannot parse %s, supported formats: \n%s", date, formats), date, 0);
-	}
-
 }

src/test/java/eu/dnetlib/dhp/schema/oaf/MergeTest.java

@@ -108,8 +108,8 @@ public class MergeTest {
 	@Test
 	public void mergeRelationTestParseException() {
 		assertThrows(DateTimeParseException.class, () -> {
-			Relation a = createRel(true, "2016 April 05");
-			Relation b = createRel(true, "2016-04-05");
+			Relation a = createRel(true, "Once upon a time ...");
+			Relation b = createRel(true, "... in a far away land");
 			a.mergeFrom(b);
 		});
 	}