diff --git a/src/bro.bif b/src/bro.bif
index 732261acc9..ee3add586d 100644
--- a/src/bro.bif
+++ b/src/bro.bif
@@ -138,12 +138,17 @@ static void do_fmt(const char*& fmt, Val* v, ODesc* d)
 			}
 
 		time_t time = time_t(v->InternalDouble());
+		struct tm t;
+
 		int is_time_fmt = *fmt == 'T';
 
+		if ( ! localtime_r(&time, &t) )
+			s.AddSP("<problem getting time>");
+
 		if ( ! strftime(out_buf, sizeof(out_buf),
 				is_time_fmt ?
 					"%Y-%m-%d-%H:%M" : "%Y-%m-%d-%H:%M:%S",
-				localtime(&time)) )
+				&t) )
 			s.AddSP("<bad time>");
 
 		else
@@ -2983,9 +2988,11 @@ function strftime%(fmt: string, d: time%) : string
 	%{
 	static char buffer[128];
 
-	time_t t = time_t(d);
+	time_t timeval = time_t(d);
+	struct tm t;
 
-	if ( strftime(buffer, 128, fmt->CheckString(), localtime(&t)) == 0 )
+	if ( ! localtime_r(&timeval, &t) ||
+	     ! strftime(buffer, 128, fmt->CheckString(), &t) )
 		return new StringVal("<strftime error>");
 
 	return new StringVal(buffer);
@@ -3003,9 +3010,10 @@ function strftime%(fmt: string, d: time%) : string
 function strptime%(fmt: string, d: string%) : time
 	%{
 	const time_t timeval = time_t();
-	struct tm t = *localtime(&timeval);
+	struct tm t;
 
-	if ( strptime(d->CheckString(), fmt->CheckString(), &t) == NULL )
+	if ( ! localtime_r(&timeval, &t) || 
+	     ! strptime(d->CheckString(), fmt->CheckString(), &t) )
 		{
 		reporter->Warning("strptime conversion failed: fmt:%s d:%s", fmt->CheckString(), d->CheckString());
 		return new Val(0.0, TYPE_TIME);
diff --git a/src/threading/formatters/JSON.cc b/src/threading/formatters/JSON.cc
index 3558baee5c..45c7be3e93 100644
--- a/src/threading/formatters/JSON.cc
+++ b/src/threading/formatters/JSON.cc
@@ -116,21 +116,28 @@ bool JSON::Describe(ODesc* desc, Value* val, const string& name) const
 				{
 				char buffer[40];
 				char buffer2[40];
-				time_t t = time_t(val->val.double_val);
+				time_t the_time = time_t(val->val.double_val);
+				struct tm t;
 
-				if ( strftime(buffer, sizeof(buffer), "%Y-%m-%dT%H:%M:%S", gmtime(&t)) > 0 )
+				desc->AddRaw("\"", 1);
+
+				if ( ! gmtime_r(&the_time, &t) ||
+				     ! strftime(buffer, sizeof(buffer), "%Y-%m-%dT%H:%M:%S", &t) )
+					{
+					GetThread()->Error(GetThread()->Fmt("json formatter: failure getting time: (%" PRIu64 ")", val->val.double_val));
+					// This was a failure, doesn't really matter what gets put here
+					// but it should probably stand out...
+					desc->Add("2000-01-01T00:00:00.000000");
+					}
+				else
 					{
 					double integ;
 					double frac = modf(val->val.double_val, &integ);
 					snprintf(buffer2, sizeof(buffer2), "%s.%06.0fZ", buffer, frac * 1000000);
-					desc->AddRaw("\"", 1);
 					desc->Add(buffer2);
-					desc->AddRaw("\"", 1);
 					}
 
-				else
-					GetThread()->Error(GetThread()->Fmt("strftime error for JSON: %" PRIu64));
-
+				desc->AddRaw("\"", 1);
 				}
 
 			else if ( timestamps == TS_EPOCH )
diff --git a/src/util.cc b/src/util.cc
index d00d4406ae..e6015cc20a 100644
--- a/src/util.cc
+++ b/src/util.cc
@@ -576,7 +576,14 @@ const char* fmt_access_time(double t)
 	{
 	static char buf[256];
 	time_t time = (time_t) t;
-	strftime(buf, sizeof(buf), "%d/%m-%H:%M", localtime(&time));
+	struct tm ts;
+
+	if ( ! localtime_r(&time, &ts) )
+		{
+		reporter->InternalError("unable to get time");
+		}
+
+	strftime(buf, sizeof(buf), "%d/%m-%H:%M", &ts);
 	return buf;
 	}