Honor SOURCE_DATE_EPOCH when exporting configuration date.
Autoconf-level patch submitted upstream on Fri Apr 15 23:07:42 UTC 2016

--- a/configure
+++ b/configure
@@ -2866,7 +2866,17 @@
 
 
 # Configuration Date
- CONFIG_DATE="`date`"
+ CONFIG_DATE="`date -u`"
+if test -n "$SOURCE_DATE_EPOCH"; then
+  CONFIG_DATE=`date -u -d "@$SOURCE_DATE_EPOCH" 2>/dev/null \
+               || date -u -r "$SOURCE_DATE_EPOCH" 2>/dev/null`
+  if test -z "$CONFIG_DATE"; then
+    as_fn_error $? "malformed SOURCE_DATE_EPOCH" "$LINENO" 5
+  fi
+fi
+cat >>confdefs.h <<_ACEOF
+#define CONFIG_DATE "$CONFIG_DATE"
+_ACEOF
 
 # Find out about the host we're building on.
 ac_aux_dir=
--- a/libdispatch/derror.c
+++ b/libdispatch/derror.c
@@ -13,7 +13,7 @@
 #endif
 
 /* Tell the user the version of netCDF. */
-static const char nc_libvers[] = PACKAGE_VERSION " of "__DATE__" "__TIME__" $";
+static const char nc_libvers[] = PACKAGE_VERSION " of "CONFIG_DATE" $";
 
 /**
 \defgroup lib_version Library Version
--- a/config.h.in
+++ b/config.h.in
@@ -393,6 +393,9 @@
 /* Define to the version of this package. */
 #undef PACKAGE_VERSION
 
+/* Define to the configuration date */
+#undef CONFIG_DATE
+
 /* The size of `double', as computed by sizeof. */
 #undef SIZEOF_DOUBLE
 
