diff --git a/http/http_server.hpp b/http/http_server.hpp
index 258193a..91de8db 100644
--- a/http/http_server.hpp
+++ b/http/http_server.hpp
@@ -67,7 +67,7 @@
         gmtime_r(&lastTimeT, &myTm);
 
         dateStr.resize(100);
-        size_t dateStrSz = strftime(&dateStr[0], 99,
+        size_t dateStrSz = strftime(dateStr.data(), dateStr.size() - 1,
                                     "%a, %d %b %Y %H:%M:%S GMT", &myTm);
         dateStr.resize(dateStrSz);
     }