diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2fd3a8c..29e0b5c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,11 @@ Proteus Changelog.
 ## Unreleased
 ### No issue
 
+**Added HEIC format**
+
+
+[1aa07d8f82ab1cc](https://github.com/noboomu/proteus/commit/1aa07d8f82ab1cc) Joshua Bauer *2021-12-24 00:44:12*
+
 **Added AVIF format**
 
 
diff --git a/proteus-core/src/main/java/io/sinistral/proteus/server/ServerResponse.java b/proteus-core/src/main/java/io/sinistral/proteus/server/ServerResponse.java
index b7272d1..c4b67b6 100644
--- a/proteus-core/src/main/java/io/sinistral/proteus/server/ServerResponse.java
+++ b/proteus-core/src/main/java/io/sinistral/proteus/server/ServerResponse.java
@@ -5,6 +5,7 @@
 import com.fasterxml.jackson.databind.ObjectWriter;
 import com.fasterxml.jackson.dataformat.xml.XmlMapper;
 import com.google.inject.Inject;
+import io.sinistral.proteus.protocol.HttpHeaders;
 import io.sinistral.proteus.protocol.MediaType;
 import io.sinistral.proteus.server.predicates.ServerPredicates;
 import io.sinistral.proteus.wrappers.JsonViewWrapper;
@@ -20,6 +21,11 @@
 import javax.ws.rs.core.Response;
 import java.net.URI;
 import java.nio.ByteBuffer;
+import java.text.SimpleDateFormat;
+import java.time.Instant;
+import java.time.ZoneId;
+import java.time.ZonedDateTime;
+import java.time.format.DateTimeFormatter;
 import java.util.Date;
 import java.util.HashMap;
 import java.util.Locale;
@@ -36,6 +42,10 @@ public class ServerResponse<T>
 {
     private static Logger log = LoggerFactory.getLogger(ServerResponse.class.getCanonicalName());
 
+    private final static String RFC1123_PATTERN = "EEE, dd MMM yyyy HH:mm:ss z";
+
+    private static final ThreadLocal<DateTimeFormatter> RFC1123_PATTERN_FORMATTER =ThreadLocal.withInitial( () -> DateTimeFormatter.ofPattern(RFC1123_PATTERN));
+
     @Inject
     protected static XmlMapper XML_MAPPER;
 
@@ -176,7 +186,6 @@ public void setStatus(Response.Status status)
         this.status = status.getStatusCode();
     }
 
-
     public ServerResponse<T> body(ByteBuffer body)
     {
         this.body = body;
@@ -219,18 +228,32 @@ public ServerResponse<T> method(String method)
     public ServerResponse<T> lastModified(Date date)
     {
         this.headers.put(Headers.LAST_MODIFIED, date.getTime());
+        this.hasHeaders = true;
         return this;
     }
 
+    /**
+     * @param instant
+     *            the instant to set
+     */
+    public ServerResponse<T> lastModified(Instant instant)
+    {
+       this.headers.put(Headers.LAST_MODIFIED,RFC1123_PATTERN_FORMATTER.get().format(ZonedDateTime.ofInstant(instant, ZoneId.of("GMT"))));
+       this.hasHeaders = true;
+       return this;
+    }
+
     public ServerResponse<T> contentLanguage(Locale locale)
     {
         this.headers.put(Headers.CONTENT_LANGUAGE, locale.toLanguageTag());
+        this.hasHeaders = true;
         return this;
     }
 
     public ServerResponse<T> contentLanguage(String language)
     {
         this.headers.put(Headers.CONTENT_LANGUAGE, language);
+        this.hasHeaders = true;
         return this;
     }
 
diff --git a/proteus-core/src/test/java/io/sinistral/proteus/test/controllers/Tests.java b/proteus-core/src/test/java/io/sinistral/proteus/test/controllers/Tests.java
index 84f2c8a..7278bf3 100644
--- a/proteus-core/src/test/java/io/sinistral/proteus/test/controllers/Tests.java
+++ b/proteus-core/src/test/java/io/sinistral/proteus/test/controllers/Tests.java
@@ -115,6 +115,8 @@ public void exchangeUserJson(HttpServerExchange exchange)
 	{  
 		response( new User(123L) ).applicationJson().send(exchange); 
 	}
+
+
 	
 	@GET 
 	@Path("exchange/user/xml")
@@ -671,7 +673,8 @@ public CompletableFuture<ServerResponse<Map<String,String>>> responseFutureNotFo
 
 		return future;
 	}
-	
+
+
 	@GET
 	@Path("response/future/user")
 	@Produces((MediaType.APPLICATION_JSON)) 
@@ -1040,5 +1043,15 @@ public ServerResponse<Map<String,Object>> multipartUploadMultipleFiles(ServerReq
 
 	}
 
+	@GET
+	@Path("headers/last-modified")
+	@Produces(MediaType.APPLICATION_JSON)
+	@Blocking
+	public ServerResponse<Map<String,String>> lastModifiedResponse(ServerRequest request)
+	{
+		return response(Map.of("key","value")).lastModified(Instant.now());
+
+	}
+
 
 }
diff --git a/proteus-core/src/test/java/io/sinistral/proteus/test/server/StandardEndpointsTest.java b/proteus-core/src/test/java/io/sinistral/proteus/test/server/StandardEndpointsTest.java
index 3b9b283..2ca06a5 100644
--- a/proteus-core/src/test/java/io/sinistral/proteus/test/server/StandardEndpointsTest.java
+++ b/proteus-core/src/test/java/io/sinistral/proteus/test/server/StandardEndpointsTest.java
@@ -578,6 +578,13 @@ public void minValueError()
 
     }
 
+    @Test
+    public void lastModified()
+    {
+
+        given().accept(ContentType.JSON).when().get("v1/tests/headers/last-modified").then().statusCode(200).body(containsString("value")).header("last-modified", CoreMatchers.anything());
+    }
+
     @Test
     public void maxValue()
     {