From db26a24f2f0086f0134c53de5d6c748f4d0cb590 Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Wed, 9 Nov 2016 05:57:05 -0800
Subject: [PATCH] Windows: fix timezone calculation

Comparing to daylight-saving time change was performed incorrectly, so
that days in the same month as a change and the hour within the day before
the switch hour were all treated as pre-switch (instead of counting
only days up to the switch as pre-switch).

Thanks to Jon Zeppieri for the repair and George Neuner for
the report.
---
 racket/src/racket/src/fun.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/racket/src/racket/src/fun.c b/racket/src/racket/src/fun.c
index bf8589cd2a..d5d7a79156 100644
--- a/racket/src/racket/src/fun.c
+++ b/racket/src/racket/src/fun.c
@@ -9875,6 +9875,8 @@ static int is_day_before(SYSTEMTIME *a, SYSTEMTIME *b)
 
   if (a->wDay < doc)
     return 1;
+  if (a->wDay > doc)
+    return 0;
 
   dtxCOMP(wHour);
   dtxCOMP(wMinute);