diff --git a/hwe/j_map_recent.php b/hwe/j_map_recent.php
index f5cd93c2..f24d0106 100644
--- a/hwe/j_map_recent.php
+++ b/hwe/j_map_recent.php
@@ -31,17 +31,12 @@ $now = time();
 if($mapInfo && ($now - $mapInfo['timestamp'] < 600)){
 	$mapEtag = $mapInfo['etag'];
 	$mapModified = $mapInfo['timestamp'];
-
-    header("Last-Modified: ".gmdate("D, d M Y H:i:s", $mapModified)." GMT");
-    header("Etag: $mapEtag");
-
-    if (
-		strtotime($_SERVER['HTTP_IF_MODIFIED_SINCE']??'2000-01-01') === $mapModified ||
-		trim($_SERVER['HTTP_IF_NONE_MATCH']??'') === $mapEtag
-	) {
-        header("HTTP/1.1 304 Not Modified");
-		die();
-	}
+    WebUtil::setCacheHeader(new APICacheResult(TimeUtil::secondsToDateTime($mapModified), $mapEtag));
+    $reqMapEtag = WebUtil::parseETag();
+    $reqModifiedSince = WebUtil::parseLastModified();
+    if($mapEtag === $reqMapEtag || $mapModified === $reqModifiedSince){
+        WebUtil::dieWithNotModified();
+    }
 
 	Json::die($mapInfo['data'], 0);
 }
@@ -76,7 +71,6 @@ $map = [
 	'data'=>$rawMap,
 ];
 $cache->save("recent_map", $map);
-header("Last-Modified: ".gmdate("D, d M Y H:i:s", $now)." GMT");
-header("Etag: $etag");
+WebUtil::setCacheHeader(new APICacheResult(TimeUtil::secondsToDateTime($now), $etag));
 
 Json::die($map['data'], 0);
\ No newline at end of file
diff --git a/hwe/sammo/API/Global/GetConst.php b/hwe/sammo/API/Global/GetConst.php
index fb14c627..6154c581 100644
--- a/hwe/sammo/API/Global/GetConst.php
+++ b/hwe/sammo/API/Global/GetConst.php
@@ -281,6 +281,13 @@ class GetConst extends \sammo\BaseAPI
         $storage = new \Nette\Caching\Storages\FileStorage($cacheDir);
         $cache = new Cache($storage);
 
+        $currentCacheKey = $this->tryCache();
+        if($modifiedSince !== null && $currentCacheKey->lastModified == $modifiedSince){
+            return null;
+        }
+        if($reqEtag !== null && $currentCacheKey->etag == $reqEtag){
+            return null;
+        }
 
         $constCache = $this->readCache($cache);
         if ($constCache !== null) {
diff --git a/src/sammo/APIHelper.php b/src/sammo/APIHelper.php
index 7e30680f..6f90af2e 100644
--- a/src/sammo/APIHelper.php
+++ b/src/sammo/APIHelper.php
@@ -9,18 +9,6 @@ class APIHelper
         //static only
     }
 
-    private static function setCacheHeader(){
-        header('cache-control: private, max-age=60');
-        header("Pragma: cache");
-        header_remove('expires');
-    }
-
-    private static function DieWithNotModified(): never{
-        static::setCacheHeader();
-        header("HTTP/1.1 304 Not Modified");
-        die();
-    }
-
     public static function launch(string $rootPath, string $actionPath, array $eParams = [], bool $loadRawInput = true)
     {
         if($loadRawInput){
@@ -73,51 +61,41 @@ class APIHelper
                 }
             }
 
-            $modifiedSince = isset($_SERVER['HTTP_IF_MODIFIED_SINCE'])
-                ? new \DateTimeImmutable($_SERVER['HTTP_IF_MODIFIED_SINCE'], new \DateTimeZone("UTC"))
-                : null;
-            $reqEtags = isset($_SERVER['HTTP_IF_NONE_MATCH']) ? trim($_SERVER['HTTP_IF_NONE_MATCH']) : null;
+            $modifiedSince = WebUtil::parseLastModified();
+            $reqEtags = WebUtil::parseETag();
 
             $result = $obj->launch($session, $modifiedSince, $reqEtags);
             if (is_string($result)) {
                 Json::dieWithReason($result);
             }
 
-            $cacheResult = $obj->tryCache();
+            $cache = $obj->tryCache();
             $setCache = false;
-            if ($cacheResult !== null) {
-                $lastModified = $cacheResult->lastModified;
-                $etag = $cacheResult->etag;
-
-                if ($lastModified !== null) {
-                    header("Last-Modified: " . gmdate("D, d M Y H:i:s", Util::toInt(TimeUtil::DateTimeToSeconds($lastModified, true))) . " GMT");
-                    $setCache = true;
-                }
-                if ($etag !== null) {
-                    header("Etag: $etag");
+            if ($cache !== null) {
+                if($cache->lastModified !== null || $cache->etag !== null){
                     $setCache = true;
+                    WebUtil::setCacheHeader($cache);
                 }
 
-                if ($modifiedSince !== null && $lastModified !== null && TimeUtil::DateIntervalToSeconds($modifiedSince->diff($lastModified)) == 0) {
-                    static::DieWithNotModified();
+
+                if ($modifiedSince !== null && $cache->lastModified !== null){
+                    $lastModifiedUnixTime = Util::toInt(TimeUtil::DateTimeToSeconds($cache->lastModified, true));
+                    $modifiedSinceUnixTime = Util::toInt(TimeUtil::DateTimeToSeconds($modifiedSince));
+                    if($lastModifiedUnixTime === $modifiedSinceUnixTime){
+                        WebUtil::dieWithNotModified();
+                    }
                 }
-                if ($reqEtags !== null && $reqEtags === $etag) {
-                    static::DieWithNotModified();
+                if ($reqEtags !== null && $reqEtags === $cache->etag) {
+                    WebUtil::dieWithNotModified();
                 }
             }
 
             if ($result === null) {
-                if ($setCache) {
-                    static::setCacheHeader();
-                }
                 Json::die([
                     'result' => true,
                     'reason' => 'success'
                 ], $setCache ? 0 : Json::NO_CACHE);
             }
-            if ($setCache) {
-                static::setCacheHeader();
-            }
             Json::die($result, $setCache ? 0 : Json::NO_CACHE);
         } catch (\Throwable $e) {
             Json::dieWithReason($e->getMessage());
diff --git a/src/sammo/WebUtil.php b/src/sammo/WebUtil.php
index 5bb24034..caed96a9 100644
--- a/src/sammo/WebUtil.php
+++ b/src/sammo/WebUtil.php
@@ -36,6 +36,48 @@ class WebUtil
         return strtolower($_SERVER['HTTP_X_REQUESTED_WITH'] ?? null) === 'xmlhttprequest';
     }
 
+    public static function setCacheHeader(?APICacheResult $cache, int $maxAge=60){
+        header_remove('expires');
+        header("Cache-Control: private, max-age={$maxAge}");
+        header("Pragma: cache");
+        if($cache->etag !== null){
+            header("ETag: \"{$cache->etag}\"");
+        }
+        if($cache->lastModified !== null){
+            $lastModifiedUnixTime = Util::toInt(TimeUtil::DateTimeToSeconds($cache->lastModified, true));
+            $lastModified = gmdate("D, d M Y H:i:s", $lastModifiedUnixTime);
+            header("Last-Modified: $lastModified GMT");
+        }
+    }
+
+    public static function dieWithNotModified(): never{
+        header("HTTP/1.1 304 Not Modified");
+        die();
+    }
+
+    public static function parseETag(): ?string{
+        $etag = $_SERVER['HTTP_IF_NONE_MATCH']??null;
+        if($etag === null){
+            return $etag;
+        }
+        $etag = trim($etag);
+        if(str_starts_with($etag, 'W/"') && str_ends_with($etag, '"')){
+            return substr($etag, 3, strlen($etag) - 4);
+        }
+        if(str_starts_with($etag, '"') && str_ends_with($etag, '"')){
+            return substr($etag, 1, strlen($etag) - 2);
+        }
+        return $etag;
+    }
+
+    public static function parseLastModified(): ?\DateTimeInterface{
+        $modifiedSinceStr = $_SERVER['HTTP_IF_MODIFIED_SINCE']??null;
+        if($modifiedSinceStr === null){
+            return null;
+        }
+        return new \DateTimeImmutable($modifiedSinceStr, new \DateTimeZone("UTC"));
+    }
+
     public static function requireAJAX(): void
     {
         if (!static::isAJAX()) {