diff --git a/CHANGES b/CHANGES
index de9aa69cb6..96abc01cf5 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,3 +1,6 @@
+4668.	[bug]		Use localtime_r and gmtime_r for thread safety.
+			[RT #45664]
+
 4667.	[cleanup]	Refactor RDATA unit tests. [RT #45610]
 
 4665.	[protocol]	Added support for ED25519 and ED448 DNSSEC signing
diff --git a/bin/dig/dig.c b/bin/dig/dig.c
index 3bc57ad442..56ddee0d05 100644
--- a/bin/dig/dig.c
+++ b/bin/dig/dig.c
@@ -27,6 +27,7 @@
 #include <isc/app.h>
 #include <isc/netaddr.h>
 #include <isc/parseint.h>
+#include <isc/platform.h>
 #include <isc/print.h>
 #include <isc/string.h>
 #include <isc/util.h>
@@ -263,7 +264,12 @@ received(int bytes, isc_sockaddr_t *from, dig_query_t *query) {
 		printf(";; Query time: %ld msec\n", (long int)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
+
 		if (strftime(time_str, sizeof(time_str),
 			     "%a %b %d %H:%M:%S %Z %Y", &tmnow) > 0U)
 			printf(";; WHEN: %s\n", time_str);
diff --git a/bin/tests/net/driver.c b/bin/tests/net/driver.c
index f57dc7976a..9a906000d8 100644
--- a/bin/tests/net/driver.c
+++ b/bin/tests/net/driver.c
@@ -23,6 +23,7 @@
 #include <stdio.h>
 #include <time.h>
 
+#include <isc/platform.h>
 #include <isc/print.h>
 #include <isc/string.h>
 #include <isc/util.h>
@@ -36,19 +37,22 @@
 const char *gettime(void);
 const char *test_result_totext(test_result_t);
 
-/*
- * Not thread safe.
- */
 const char *
 gettime(void) {
 	static char now[512];
 	time_t t;
+#if defined(ISC_PLATFORM_USETHREADS) && !defined(WIN32)
+	struct tm tm;
+#endif
 
 	(void)time(&t);
 
-	strftime(now, sizeof(now) - 1,
-		 "%A %d %B %H:%M:%S %Y",
-		 localtime(&t));
+#if defined(ISC_PLATFORM_USETHREADS) && !defined(WIN32)
+	strftime(now, sizeof(now) - 1, "%A %d %B %H:%M:%S %Y",
+		 localtime_r(&t, &tm));
+#else
+	strftime(now, sizeof(now) - 1, "%A %d %B %H:%M:%S %Y", localtime(&t));
+#endif
 
 	return (now);
 }
diff --git a/lib/dns/update.c b/lib/dns/update.c
index 10910ca507..9e44f0052b 100644
--- a/lib/dns/update.c
+++ b/lib/dns/update.c
@@ -22,6 +22,7 @@
 #include <isc/magic.h>
 #include <isc/mem.h>
 #include <isc/netaddr.h>
+#include <isc/platform.h>
 #include <isc/print.h>
 #include <isc/serial.h>
 #include <isc/stats.h>
@@ -2027,6 +2028,23 @@ dns_update_signaturesinc(dns_update_log_t *log, dns_zone_t *zone, dns_db_t *db,
 	return (result);
 }
 
+<<<<<<< HEAD
+=======
+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);
+}
+
+>>>>>>> 4162d3b36d... 4668.   [bug]           Use localtime_r and gmtime_r for thread safety.
 isc_uint32_t
 dns_update_soaserial(isc_uint32_t serial, dns_updatemethod_t method) {
 	isc_stdtime_t now;
diff --git a/lib/isc/unix/time.c b/lib/isc/unix/time.c
index 400bbf8f3b..d10051a124 100644
--- a/lib/isc/unix/time.c
+++ b/lib/isc/unix/time.c
@@ -30,6 +30,7 @@
 #include <sys/time.h>	/* Required for struct timeval on some platforms. */
 
 #include <isc/log.h>
+#include <isc/platform.h>
 #include <isc/print.h>
 #include <isc/strerror.h>
 #include <isc/string.h>
@@ -384,11 +385,18 @@ void
 isc_time_formattimestamp(const isc_time_t *t, char *buf, unsigned int len) {
 	time_t now;
 	unsigned int flen;
+#ifdef ISC_PLATFORM_USETHREADS
+	struct tm tm;
+#endif
 
 	REQUIRE(len > 0);
 
 	now = (time_t) t->seconds;
+#ifdef ISC_PLATFORM_USETHREADS
+	flen = strftime(buf, len, "%d-%b-%Y %X", localtime_r(&now, &tm));
+#else
 	flen = strftime(buf, len, "%d-%b-%Y %X", localtime(&now));
+#endif
 	INSIST(flen < len);
 	if (flen != 0)
 		snprintf(buf + flen, len - flen,
@@ -401,6 +409,9 @@ void
 isc_time_formathttptimestamp(const isc_time_t *t, char *buf, unsigned int len) {
 	time_t now;
 	unsigned int flen;
+#ifdef ISC_PLATFORM_USETHREADS
+	struct tm tm;
+#endif
 
 	REQUIRE(len > 0);
 
@@ -408,7 +419,12 @@ isc_time_formathttptimestamp(const isc_time_t *t, char *buf, unsigned int len) {
 	 * 5 spaces, 1 comma, 3 GMT, 2 %d, 4 %Y, 8 %H:%M:%S, 3+ %a, 3+ %b (29+)
 	 */
 	now = (time_t)t->seconds;
+#ifdef ISC_PLATFORM_USETHREADS
+	flen = strftime(buf, len, "%a, %d %b %Y %H:%M:%S GMT",
+			gmtime_r(&now, &tm));
+#else
 	flen = strftime(buf, len, "%a, %d %b %Y %H:%M:%S GMT", gmtime(&now));
+#endif
 	INSIST(flen < len);
 }
 
@@ -434,10 +450,17 @@ void
 isc_time_formatISO8601(const isc_time_t *t, char *buf, unsigned int len) {
 	time_t now;
 	unsigned int flen;
+#ifdef ISC_PLATFORM_USETHREADS
+	struct tm tm;
+#endif
 
 	REQUIRE(len > 0);
 
 	now = (time_t)t->seconds;
+#ifdef ISC_PLATFORM_USETHREADS
+	flen = strftime(buf, len, "%Y-%m-%dT%H:%M:%SZ", gmtime_r(&now, &tm));
+#else
 	flen = strftime(buf, len, "%Y-%m-%dT%H:%M:%SZ", gmtime(&now));
+#endif
 	INSIST(flen < len);
 }
diff --git a/lib/tests/t_api.c b/lib/tests/t_api.c
index bfc68ee080..f01fbffb4a 100644
--- a/lib/tests/t_api.c
+++ b/lib/tests/t_api.c
@@ -39,6 +39,7 @@
 
 #include <isc/boolean.h>
 #include <isc/commandline.h>
+#include <isc/platform.h>
 #include <isc/print.h>
 #include <isc/string.h>
 #include <isc/mem.h>
@@ -605,9 +606,16 @@ t_getdate(char *buf, size_t buflen) {
 	size_t		n;
 	time_t		t;
 	struct tm	*p;
+#if defined(ISC_PLATFORM_USETHREADS) && !defined(WIN32)
+	struct tm	tm;
+#endif
 
 	t = time(NULL);
+#if defined(ISC_PLATFORM_USETHREADS) && !defined(WIN32)
+	p = localtime_r(&t, &tm);
+#else
 	p = localtime(&t);
+#endif
 	n = strftime(buf, buflen - 1, "%A %d %B %H:%M:%S %Y\n", p);
 	return(n != 0U ? buf : NULL);
 }