diff --git a/bin/dig/dig.c b/bin/dig/dig.c
index 706299e75a..996cbb9495 100644
--- a/bin/dig/dig.c
+++ b/bin/dig/dig.c
@@ -277,11 +277,7 @@ received(unsigned int bytes, isc_sockaddr_t *from, dig_query_t *query) {
 			printf(";; Query time: %ld msec\n", (long) diff / 1000);
 		printf(";; SERVER: %s(%s)\n", fromtext, query->servname);
 		time(&tnow);
-#if defined(ISC_PLATFORM_USETHREADS) && !defined(WIN32)
 		(void)localtime_r(&tnow, &tmnow);
-#else
-		tmnow  = *localtime(&tnow);
-#endif
 
 #ifdef WIN32
 		/*
diff --git a/bin/dnssec/dnssec-settime.c b/bin/dnssec/dnssec-settime.c
index 62ef8422c7..e128ee7b4b 100644
--- a/bin/dnssec/dnssec-settime.c
+++ b/bin/dnssec/dnssec-settime.c
@@ -121,15 +121,16 @@ printtime(dst_key_t *key, int type, const char *tag, bool epoch,
 	} else if (epoch) {
 		fprintf(stream, "%d\n", (int) when);
 	} else {
-		time_t now = (time_t)when;
-#ifdef _MSC_VER
-		struct tm *tm = localtime(&now); /* Thread specific. */
-#else
+		time_t now = when;
 		struct tm t, *tm = localtime_r(&now, &t);
-#endif
 		unsigned int flen;
 		char timebuf[80];
 
+		if (tm == NULL) {
+			fprintf(stream, "INVALID\n");
+			return;
+		}
+
 		flen = strftime(timebuf, sizeof(timebuf),
 				"%a %b %e %H:%M:%S %Y", tm);
 		INSIST(flen > 0U && flen < sizeof(timebuf));
diff --git a/bin/dnssec/dnssec-signzone.c b/bin/dnssec/dnssec-signzone.c
index 8d93be83fa..cd235b2e8f 100644
--- a/bin/dnssec/dnssec-signzone.c
+++ b/bin/dnssec/dnssec-signzone.c
@@ -2955,16 +2955,13 @@ writeset(const char *prefix, dns_rdatatype_t type) {
 static void
 print_time(FILE *fp) {
 	time_t currenttime = time(NULL);
-#ifdef _MSC_VER
-	struct tm *tm = localtime(&currenttime); /* Thread specific. */
-#else
 	struct tm t, *tm = localtime_r(&currenttime, &t);
-#endif
 	unsigned int flen;
 	char timebuf[80];
 
-	if (outputformat != dns_masterformat_text)
+	if (tm == NULL || outputformat != dns_masterformat_text) {
 		return;
+	}
 
 	flen = strftime(timebuf, sizeof(timebuf), "%a %b %e %H:%M:%S %Y", tm);
 	INSIST(flen > 0U && flen < sizeof(timebuf));
diff --git a/lib/dns/gen-win32.h b/lib/dns/gen-win32.h
index 4791032650..18a98950c3 100644
--- a/lib/dns/gen-win32.h
+++ b/lib/dns/gen-win32.h
@@ -62,6 +62,7 @@
 #include <stdbool.h>
 #include <stdio.h>
 #include <string.h>
+#include <time.h>
 #include <windows.h>
 
 #include <isc/lang.h>
@@ -268,6 +269,16 @@ end_directory(isc_dir_t *dir) {
 		FindClose(dir->handle);
 }
 
+inline struct tm *
+gmtime_r(const time_t *clock, struct tm *result) {
+	errno_t ret = gmtime_s(result, clock);
+	if (ret != 0) {
+		errno = ret;
+		return (NULL);
+	}
+	return (result);
+}
+
 ISC_LANG_ENDDECLS
 
 #endif /* DNS_GEN_WIN32_H */
diff --git a/lib/dns/gen.c b/lib/dns/gen.c
index 589cd20526..fe6fef0de2 100644
--- a/lib/dns/gen.c
+++ b/lib/dns/gen.c
@@ -689,11 +689,7 @@ main(int argc, char **argv) {
 	}
 
 	if (now != -1) {
-#ifdef _MSC_VER
-		struct tm *tm = gmtime(&now); /* Thread specific. */
-#else
 		struct tm t, *tm = gmtime_r(&now, &t);
-#endif
 
 		if (tm != NULL && tm->tm_year > 104) {
 			n = snprintf(year, sizeof(year), "-%d",
diff --git a/lib/dns/update.c b/lib/dns/update.c
index f735642991..085cc5509c 100644
--- a/lib/dns/update.c
+++ b/lib/dns/update.c
@@ -2082,16 +2082,12 @@ dns_update_signaturesinc(dns_update_log_t *log, dns_zone_t *zone, dns_db_t *db,
 
 static isc_stdtime_t
 epoch_to_yyyymmdd(time_t when) {
-	struct tm *tm;
-
-#if defined(ISC_PLATFORM_USETHREADS) && !defined(WIN32)
-	struct tm tm0;
-	tm = localtime_r(&when, &tm0);
-#else
-	tm = localtime(&when);
-#endif
-	return (((tm->tm_year + 1900) * 10000) +
-		((tm->tm_mon + 1) * 100) + tm->tm_mday);
+	struct tm t, *tm = localtime_r(&when, &t);
+	if (tm == NULL) {
+		return (0);
+	}
+	return (((tm->tm_year + 1900) * 10000) + ((tm->tm_mon + 1) * 100) +
+		tm->tm_mday);
 }
 
 uint32_t
diff --git a/lib/isc/win32/include/isc/time.h b/lib/isc/win32/include/isc/time.h
index 486f527c60..8494736fea 100644
--- a/lib/isc/win32/include/isc/time.h
+++ b/lib/isc/win32/include/isc/time.h
@@ -13,6 +13,7 @@
 #ifndef ISC_TIME_H
 #define ISC_TIME_H 1
 
+#include <errno.h>
 #include <inttypes.h>
 #include <stdbool.h>
 #include <windows.h>
@@ -20,6 +21,30 @@
 #include <isc/lang.h>
 #include <isc/types.h>
 
+/***
+ *** POSIX Shims
+ ***/
+
+inline struct tm *
+gmtime_r(const time_t *clock, struct tm *result) {
+	errno_t ret = gmtime_s(result, clock);
+	if (ret != 0) {
+		errno = ret;
+		return (NULL);
+	}
+	return (result);
+}
+
+inline struct tm *
+localtime_r(const time_t *clock, struct tm *result) {
+	errno_t ret = localtime_s(result, clock);
+	if (ret != 0) {
+		errno = ret;
+		return (NULL);
+	}
+	return (result);
+}
+
 /***
  *** Intervals
  ***/