diff --git a/scm-webapp/src/main/java/sonia/scm/api/rest/JSONContextResolver.java b/scm-webapp/src/main/java/sonia/scm/api/rest/JSONContextResolver.java
index 9ea7acb00a..1b4f41d9ab 100644
--- a/scm-webapp/src/main/java/sonia/scm/api/rest/JSONContextResolver.java
+++ b/scm-webapp/src/main/java/sonia/scm/api/rest/JSONContextResolver.java
@@ -33,6 +33,7 @@ package sonia.scm.api.rest;
 import com.fasterxml.jackson.databind.AnnotationIntrospector;
 import com.fasterxml.jackson.databind.DeserializationFeature;
 import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.SerializationFeature;
 import com.fasterxml.jackson.databind.introspect.AnnotationIntrospectorPair;
 import com.fasterxml.jackson.databind.introspect.JacksonAnnotationIntrospector;
 import com.fasterxml.jackson.databind.type.TypeFactory;
@@ -63,6 +64,8 @@ public final class JSONContextResolver implements ContextResolver<ObjectMapper>
       .registerModule(new JavaTimeModule());
     mapper.setAnnotationIntrospector(createAnnotationIntrospector());
     mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
+    mapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
+    mapper.configure(SerializationFeature.WRITE_DATES_WITH_ZONE_ID, true);
   }
   
   private AnnotationIntrospector createAnnotationIntrospector() {
diff --git a/scm-webapp/src/main/java/sonia/scm/api/v2/resources/UserCollectionResource.java b/scm-webapp/src/main/java/sonia/scm/api/v2/resources/UserCollectionResource.java
index 2dbc8e8ef7..7bcf517edc 100644
--- a/scm-webapp/src/main/java/sonia/scm/api/v2/resources/UserCollectionResource.java
+++ b/scm-webapp/src/main/java/sonia/scm/api/v2/resources/UserCollectionResource.java
@@ -19,6 +19,7 @@ import java.util.List;
 import java.util.stream.Collectors;
 
 @Singleton
+@Produces(MediaType.APPLICATION_JSON)
 public class UserCollectionResource extends AbstractManagerResource<User, UserException> {
   private final UserDto2UserMapper dtoToUserMapper;
   private final User2UserDtoMapper userToDtoMapper;
@@ -48,7 +49,6 @@ public class UserCollectionResource extends AbstractManagerResource<User, UserEx
     @ResponseCode(code = 403, condition = "forbidden, the current user has no admin privileges"),
     @ResponseCode(code = 500, condition = "internal server error")
   })
-  @Produces({MediaType.APPLICATION_JSON, MediaType.APPLICATION_XML})
   public Response getAll(@Context Request request, @Context UriInfo uriInfo, @DefaultValue("0")
   @QueryParam("start") int start, @DefaultValue("-1")
   @QueryParam("limit") int limit, @QueryParam("sortby") String sortby,
@@ -69,7 +69,6 @@ public class UserCollectionResource extends AbstractManagerResource<User, UserEx
     @ResponseCode(code = 500, condition = "internal server error")
   })
   @TypeHint(TypeHint.NO_CONTENT.class)
-  @Produces({MediaType.APPLICATION_JSON, MediaType.APPLICATION_XML})
   public Response create(@Context UriInfo uriInfo, UserDto userDto) throws IOException, UserException {
     User user = dtoToUserMapper.userDtoToUser(userDto, "");
     manager.create(user);
diff --git a/scm-webapp/src/main/java/sonia/scm/api/v2/resources/UserDto.java b/scm-webapp/src/main/java/sonia/scm/api/v2/resources/UserDto.java
index 4e90e0e68f..9b43d98ec8 100644
--- a/scm-webapp/src/main/java/sonia/scm/api/v2/resources/UserDto.java
+++ b/scm-webapp/src/main/java/sonia/scm/api/v2/resources/UserDto.java
@@ -1,13 +1,15 @@
 package sonia.scm.api.v2.resources;
 
+import com.fasterxml.jackson.annotation.JsonInclude;
+import com.fasterxml.jackson.annotation.JsonProperty;
 import lombok.Data;
 
-import javax.xml.bind.annotation.XmlElement;
 import java.time.Instant;
 import java.util.Map;
 import java.util.Optional;
 
 @Data
+@JsonInclude(JsonInclude.Include.NON_EMPTY)
 public class UserDto {
   private boolean active;
   private boolean admin;
@@ -19,6 +21,6 @@ public class UserDto {
   private String password;
   private String type;
 
-  @XmlElement(name = "_links")
+  @JsonProperty("_links")
   private Map<String, Link> links;
 }
diff --git a/scm-webapp/src/main/java/sonia/scm/api/v2/resources/UserSubResource.java b/scm-webapp/src/main/java/sonia/scm/api/v2/resources/UserSubResource.java
index 1d6bacef3f..bdcecabe96 100644
--- a/scm-webapp/src/main/java/sonia/scm/api/v2/resources/UserSubResource.java
+++ b/scm-webapp/src/main/java/sonia/scm/api/v2/resources/UserSubResource.java
@@ -1,6 +1,7 @@
 package sonia.scm.api.v2.resources;
 
 import com.google.inject.Inject;
+import com.google.inject.Singleton;
 import com.webcohesion.enunciate.metadata.rs.ResponseCode;
 import com.webcohesion.enunciate.metadata.rs.StatusCodes;
 import com.webcohesion.enunciate.metadata.rs.TypeHint;
@@ -15,6 +16,8 @@ import javax.ws.rs.*;
 import javax.ws.rs.core.*;
 import java.util.Collection;
 
+@Singleton
+@Produces(MediaType.APPLICATION_JSON)
 public class UserSubResource extends AbstractManagerResource<User, UserException> {
   private final UserDto2UserMapper dtoToUserMapper;
   private final User2UserDtoMapper userToDtoMapper;
@@ -35,7 +38,6 @@ public class UserSubResource extends AbstractManagerResource<User, UserException
     @ResponseCode(code = 404, condition = "not found, no group with the specified id/name available"),
     @ResponseCode(code = 500, condition = "internal server error")
   })
-  @Produces({MediaType.APPLICATION_JSON, MediaType.APPLICATION_XML})
   public Response get(@Context Request request, @Context UriInfo uriInfo, @PathParam("id") String id)
   {
     if (SecurityUtils.getSubject().hasRole(Role.ADMIN))
@@ -58,7 +60,6 @@ public class UserSubResource extends AbstractManagerResource<User, UserException
     @ResponseCode(code = 500, condition = "internal server error")
   })
   @TypeHint(TypeHint.NO_CONTENT.class)
-  @Produces({MediaType.APPLICATION_JSON, MediaType.APPLICATION_XML})
   public Response update(@Context UriInfo uriInfo,
     @PathParam("id") String name, UserDto userDto)
   {
diff --git a/scm-webapp/src/test/java/sonia/scm/api/rest/JSONContextResolverTest.java b/scm-webapp/src/test/java/sonia/scm/api/rest/JSONContextResolverTest.java
index f5843ba380..dabf75b2b0 100644
--- a/scm-webapp/src/test/java/sonia/scm/api/rest/JSONContextResolverTest.java
+++ b/scm-webapp/src/test/java/sonia/scm/api/rest/JSONContextResolverTest.java
@@ -30,15 +30,26 @@
  */
 package sonia.scm.api.rest;
 
+import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.ObjectMapper;
-import java.io.IOException;
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.NoArgsConstructor;
+import org.junit.Test;
+
 import javax.xml.bind.annotation.XmlAccessType;
 import javax.xml.bind.annotation.XmlAccessorType;
 import javax.xml.bind.annotation.XmlElement;
 import javax.xml.bind.annotation.XmlRootElement;
-import org.junit.Test;
+import java.io.IOException;
+import java.time.Instant;
+import java.time.LocalDateTime;
+import java.time.ZoneOffset;
+import java.time.format.DateTimeFormatter;
+import java.util.Optional;
+
 import static org.junit.Assert.*;
 
 /**
@@ -47,7 +58,7 @@ import static org.junit.Assert.*;
  * @author Sebastian Sdorra
  */
 public class JSONContextResolverTest {
-  
+
   private final ObjectMapper mapper = new JSONContextResolver().getContext(Object.class);
 
   /**
@@ -139,4 +150,47 @@ public class JSONContextResolverTest {
     }
     
   }
+
+  @Test
+  public void shouldWriteDate() throws JsonProcessingException {
+    DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm");
+    LocalDateTime dateTime = LocalDateTime.parse("1998-06-13 14:40", formatter);
+
+    DateSample value = new DateSample(dateTime.toInstant(ZoneOffset.UTC));
+
+    assertEquals("{\"date\":\"1998-06-13T14:40:00Z\"}", mapper.writeValueAsString(value));
+  }
+
+  @Data @AllArgsConstructor @NoArgsConstructor
+  private static class DateSample {
+    private Instant date;
+  }
+
+  @Test
+  public void shouldNotWriteEmptyOptionals() throws JsonProcessingException {
+    OptionalSample emptyValue = new OptionalSample(Optional.empty());
+    OptionalSample presentValue = new OptionalSample(Optional.of("world"));
+
+    assertEquals("{}", mapper.writeValueAsString(emptyValue));
+    assertEquals("{\"value\":\"world\"}", mapper.writeValueAsString(presentValue));
+  }
+
+  @Test
+  public void shouldReadEmptyOptionals() throws IOException {
+    OptionalSample value = mapper.readValue("{}", OptionalSample.class);
+    assertNotNull("Optional should not be null", value.getValue());
+    assertFalse("Optional should be set as empty", value.getValue().isPresent());
+  }
+
+  @Test
+  public void shouldReadNonEmptyOptionals() throws IOException {
+    OptionalSample value = mapper.readValue("{\"value\":\"world\"}", OptionalSample.class);
+    assertEquals("world", value.getValue().get());
+  }
+
+  @Data @AllArgsConstructor @NoArgsConstructor
+  private static class OptionalSample {
+    @JsonInclude(JsonInclude.Include.NON_EMPTY)
+    private Optional<String> value;
+  }
 }