diff --git a/src/time.c b/src/time.c
index 272a5b5..89ff08b 100644
--- a/src/time.c
+++ b/src/time.c
@@ -314,6 +314,7 @@
     char_u	*enc;
 
     CLEAR_FIELD(tmval);
+    tmval.tm_isdst = -1;
     fmt = tv_get_string(&argvars[0]);
     str = tv_get_string(&argvars[1]);