--- a/src/core/ngx_times.c
+++ b/src/core/ngx_times.c
@@ -27,6 +27,18 @@ volatile ngx_time_t     *ngx_cached_time
 volatile ngx_str_t       ngx_cached_err_log_time;
 volatile ngx_str_t       ngx_cached_http_time;
 volatile ngx_str_t       ngx_cached_http_log_time;
+volatile ngx_str_t       ngx_cached_http_log_iso8601;
+
+#if !(NGX_WIN32)
+
+/*
+ * locatime() and localtime_r() are not Async-Signal-Safe functions, therefore,
+ * they must not be called by a signal handler, so we use the cached
+ * GMT offset value. Fortunately the value is changed only two times a year.
+ */
+
+static ngx_int_t         cached_gmtoff;
+#endif
 
 static ngx_time_t        cached_time[NGX_TIME_SLOTS];
 static u_char            cached_err_log_time[NGX_TIME_SLOTS]
@@ -35,6 +47,8 @@ static u_char            cached_http_tim
                                     [sizeof("Mon, 28 Sep 1970 06:00:00 GMT")];
 static u_char            cached_http_log_time[NGX_TIME_SLOTS]
                                     [sizeof("28/Sep/1970:12:00:00 +0600")];
+static u_char            cached_http_log_iso8601[NGX_TIME_SLOTS]
+                                    [sizeof("1970-09-28T12:00:00+06:00")];
 
 
 static char  *week[] = { "Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat" };
@@ -47,18 +61,21 @@ ngx_time_init(void)
     ngx_cached_err_log_time.len = sizeof("1970/09/28 12:00:00") - 1;
     ngx_cached_http_time.len = sizeof("Mon, 28 Sep 1970 06:00:00 GMT") - 1;
     ngx_cached_http_log_time.len = sizeof("28/Sep/1970:12:00:00 +0600") - 1;
+    ngx_cached_http_log_iso8601.len = sizeof("1970-09-28T12:00:00+06:00") - 1;
 
     ngx_cached_time = &cached_time[0];
 
-    ngx_time_update(0, 0);
+    ngx_time_update();
 }
 
 
 void
-ngx_time_update(time_t sec, ngx_uint_t msec)
+ngx_time_update(void)
 {
-    u_char          *p0, *p1, *p2;
+    u_char          *p0, *p1, *p2, *p3;
     ngx_tm_t         tm, gmt;
+    time_t           sec;
+    ngx_uint_t       msec;
     ngx_time_t      *tp;
     struct timeval   tv;
 
@@ -66,12 +83,10 @@ ngx_time_update(time_t sec, ngx_uint_t m
         return;
     }
 
-    if (sec == 0) {
-        ngx_gettimeofday(&tv);
+    ngx_gettimeofday(&tv);
 
-        sec = tv.tv_sec;
-        msec = tv.tv_usec / 1000;
-    }
+    sec = tv.tv_sec;
+    msec = tv.tv_usec / 1000;
 
     ngx_current_msec = (ngx_msec_t) sec * 1000 + msec;
 
@@ -112,12 +127,14 @@ ngx_time_update(time_t sec, ngx_uint_t m
 #elif (NGX_HAVE_GMTOFF)
 
     ngx_localtime(sec, &tm);
-    tp->gmtoff = (ngx_int_t) (tm.ngx_tm_gmtoff / 60);
+    cached_gmtoff = (ngx_int_t) (tm.ngx_tm_gmtoff / 60);
+    tp->gmtoff = cached_gmtoff;
 
 #else
 
     ngx_localtime(sec, &tm);
-    tp->gmtoff = ngx_timezone(tm.ngx_tm_isdst);
+    cached_gmtoff = ngx_timezone(tm.ngx_tm_isdst);
+    tp->gmtoff = cached_gmtoff;
 
 #endif
 
@@ -139,6 +156,15 @@ ngx_time_update(time_t sec, ngx_uint_t m
                        tp->gmtoff < 0 ? '-' : '+',
                        ngx_abs(tp->gmtoff / 60), ngx_abs(tp->gmtoff % 60));
 
+    p3 = &cached_http_log_iso8601[slot][0];
+
+    (void) ngx_sprintf(p3, "%4d-%02d-%02dT%02d:%02d:%02d%c%02d:%02d",
+                       tm.ngx_tm_year, tm.ngx_tm_mon,
+                       tm.ngx_tm_mday, tm.ngx_tm_hour,
+                       tm.ngx_tm_min, tm.ngx_tm_sec,
+                       tp->gmtoff < 0 ? '-' : '+',
+                       ngx_abs(tp->gmtoff / 60), ngx_abs(tp->gmtoff % 60));
+
 
     ngx_memory_barrier();
 
@@ -146,11 +172,63 @@ ngx_time_update(time_t sec, ngx_uint_t m
     ngx_cached_http_time.data = p0;
     ngx_cached_err_log_time.data = p1;
     ngx_cached_http_log_time.data = p2;
+    ngx_cached_http_log_iso8601.data = p3;
 
     ngx_unlock(&ngx_time_lock);
 }
 
 
+#if !(NGX_WIN32)
+
+void
+ngx_time_sigsafe_update(void)
+{
+    u_char          *p;
+    ngx_tm_t         tm;
+    time_t           sec;
+    ngx_time_t      *tp;
+    struct timeval   tv;
+
+    if (!ngx_trylock(&ngx_time_lock)) {
+        return;
+    }
+
+    ngx_gettimeofday(&tv);
+
+    sec = tv.tv_sec;
+
+    tp = &cached_time[slot];
+
+    if (tp->sec == sec) {
+        ngx_unlock(&ngx_time_lock);
+        return;
+    }
+
+    if (slot == NGX_TIME_SLOTS - 1) {
+        slot = 0;
+    } else {
+        slot++;
+    }
+
+    ngx_gmtime(sec + cached_gmtoff * 60, &tm);
+
+    p = &cached_err_log_time[slot][0];
+
+    (void) ngx_sprintf(p, "%4d/%02d/%02d %02d:%02d:%02d",
+                       tm.ngx_tm_year, tm.ngx_tm_mon,
+                       tm.ngx_tm_mday, tm.ngx_tm_hour,
+                       tm.ngx_tm_min, tm.ngx_tm_sec);
+
+    ngx_memory_barrier();
+
+    ngx_cached_err_log_time.data = p;
+
+    ngx_unlock(&ngx_time_lock);
+}
+
+#endif
+
+
 u_char *
 ngx_http_time(u_char *buf, time_t t)
 {