diff --git a/libsgp4/DateTime.h b/libsgp4/DateTime.h
index 0ddc35e..9c98301 100644
--- a/libsgp4/DateTime.h
+++ b/libsgp4/DateTime.h
@@ -22,6 +22,7 @@
 #include <iostream>
 #include <sstream>
 #include <chrono>
+#include <algorithm>
 #include <cassert>
 #include "TimeSpan.h"
 #include "Util.h"