diff --git a/ChangeLog b/ChangeLog
index 03144f045..c97758ea6 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2017-01-04  Dirk Eddelbuettel  <edd@debian.org>
+
+        * src/Date.cpp (Rcpp): Protect assignment to tm_gmtoff to not being
+        under MinGW; could potentially bite other too-limited systems
+
+        * inst/unitTests/runit.Date.R (test.Datetime.formating): Do not set TZ
+        when running test, only set digits option
+
 2017-01-01  Dirk Eddelbuettel  <edd@debian.org>
 
         * inst/unitTests/runit.Date.R (test.mktime, test.gmtime): New tests
diff --git a/inst/unitTests/runit.Date.R b/inst/unitTests/runit.Date.R
old mode 100644
new mode 100755
index a6193aae5..22feb92ff
--- a/inst/unitTests/runit.Date.R
+++ b/inst/unitTests/runit.Date.R
@@ -217,9 +217,6 @@ if (.runThisTest) {
     }
 
     test.Datetime.formating <- function() {
-        oldTZ <- Sys.getenv("TZ")
-        Sys.setenv(TZ="America/Chicago")
-
         olddigits <- getOption("digits.secs")
         options("digits.secs"=6)
 
@@ -234,7 +231,6 @@ if (.runThisTest) {
                     format(d, "%Y-%m-%d %H:%M:%OS"),
                     msg="Datetime.formating.ostream")
 
-        Sys.setenv(TZ=oldTZ)
         options("digits.secs"=olddigits)
     }
 
diff --git a/src/Date.cpp b/src/Date.cpp
index cb3aff202..e2b073c80 100644
--- a/src/Date.cpp
+++ b/src/Date.cpp
@@ -1347,9 +1347,10 @@ struct tzhead {
             idays -= ip[tmp->tm_mon];
         tmp->tm_mday = (int) (idays + 1);
         tmp->tm_isdst = 0;
-        //#ifdef HAVE_TM_GMTOFF
+#if ! (defined(__MINGW32__) || defined(__MINGW64__))
+//#ifdef HAVE_TM_GMTOFF
         tmp->tm_gmtoff = offset;
-        //#endif
+#endif
         return tmp;
     }