diff --git a/docs/05.PORT-API.md b/docs/05.PORT-API.md
index 41c72a3252..cf66fcf93b 100644
--- a/docs/05.PORT-API.md
+++ b/docs/05.PORT-API.md
@@ -76,27 +76,25 @@ void jerry_port_log (jerry_log_level_t level, const char *fmt, ...);
 
 ```c
 /**
- * Jerry time zone structure
- */
-typedef struct
-{
-  int offset;                /**< minutes from west */
-  int daylight_saving_time;  /**< daylight saving time (1 - DST applies, 0 - not on DST) */
-} jerry_time_zone_t;
-
-/**
- * Get timezone and daylight saving data
+ * Get local timezone adjustment, in milliseconds, for the given timestamp.
+ * The timestamp can be specified in either utc or local time, depending on
+ * the value of is_utc. Adding the value returned from this function to
+ * a timestamp in utc time should result in local time for the current timezone.
  *
  * Note:
  *      This port function is called by jerry-core when
  *      CONFIG_DISABLE_DATE_BUILTIN is _not_ defined. Otherwise this function is
  *      not used.
  *
- * @param[out] tz_p time zone structure to fill.
- * @return true  - if success
- *         false - otherwise
+ * @param js_time_ms The timestamp we want an offset for (could be now, in
+ *                   the future, or in the past)
+ * @param is_utc Is the given timestamp in UTC time? If false, it is in local
+                 time.
+ *
+ * @return offset in milliseconds, if available
+ *.        0 if not available / we are in UTC.
  */
-bool jerry_port_get_time_zone (jerry_time_zone_t *tz_p);
+bool jerry_port_get_local_tza (double js_time_ms, bool is_utc);
 
 /**
  * Get system time
@@ -198,27 +196,20 @@ jerry_port_log (jerry_log_level_t level, /**< log level */
 #include "jerryscript-port.h"
 
 /**
- * Default implementation of jerry_port_get_time_zone.
+ * Default implementation of jerry_port_get_local_tza.
  */
-bool jerry_port_get_time_zone (jerry_time_zone_t *tz_p)
+double jerry_port_get_local_tza (double unix_ms, /**< ms since unix epoch */
+                                 bool is_utc)    /**< is the time above in utc? */
 {
-  struct timeval tv;
-  struct timezone tz;
-
-  /* gettimeofday may not fill tz, so zero-initializing */
-  tz.tz_minuteswest = 0;
-  tz.tz_dsttime = 0;
-
-  if (gettimeofday (&tv, &tz) != 0)
-  {
-    return false;
+  struct tm tm;
+  time_t now = (time_t)(unix_ms / 1000);
+  localtime_r(&now, &tm);
+  if (!is_utc) {
+    now -= tm.tm_gmtoff;
+    localtime_r(&now, &tm);
   }
-
-  tz_p->offset = tz.tz_minuteswest;
-  tz_p->daylight_saving_time = tz.tz_dsttime > 0 ? 1 : 0;
-
-  return true;
-} /* jerry_port_get_time_zone */
+  return tm.tm_gmtoff * 1000;
+} /* jerry_port_get_local_tza */
 
 /**
  * Default implementation of jerry_port_get_current_time.
diff --git a/jerry-core/ecma/builtin-objects/ecma-builtin-helpers-date.c b/jerry-core/ecma/builtin-objects/ecma-builtin-helpers-date.c
index 084b0ff479..2e1fba2d95 100644
--- a/jerry-core/ecma/builtin-objects/ecma-builtin-helpers-date.c
+++ b/jerry-core/ecma/builtin-objects/ecma-builtin-helpers-date.c
@@ -301,41 +301,6 @@ ecma_date_week_day (ecma_number_t time) /**< time value */
   return (week_day < 0) ? (7 + week_day) : week_day;
 } /* ecma_date_week_day */
 
-/**
- * Helper function to get local time zone adjustment.
- *
- * See also:
- *          ECMA-262 v5, 15.9.1.7
- *
- * @return local time zone adjustment
- */
-static inline ecma_number_t JERRY_ATTR_ALWAYS_INLINE
-ecma_date_local_tza (jerry_time_zone_t *tz) /**< time zone information */
-{
-  return tz->offset * -ECMA_DATE_MS_PER_MINUTE;
-} /* ecma_date_local_tza */
-
-/**
- * Helper function to get the daylight saving time adjustment.
- *
- * See also:
- *          ECMA-262 v5, 15.9.1.8
- *
- * @return daylight saving time adjustment
- */
-static inline ecma_number_t JERRY_ATTR_ALWAYS_INLINE
-ecma_date_daylight_saving_ta (jerry_time_zone_t *tz, /**< time zone information */
-                              ecma_number_t time) /**< time value */
-{
-  JERRY_ASSERT (!ecma_number_is_nan (time));
-
-  /*
-   * TODO: Fix daylight saving calculation.
-   *       https://github.com/jerryscript-project/jerryscript/issues/1661
-   */
-  return tz->daylight_saving_time * ECMA_DATE_MS_PER_HOUR;
-} /* ecma_date_daylight_saving_ta */
-
 /**
  * Helper function to get local time from UTC.
  *
@@ -347,15 +312,7 @@ ecma_date_daylight_saving_ta (jerry_time_zone_t *tz, /**< time zone information
 inline ecma_number_t JERRY_ATTR_ALWAYS_INLINE
 ecma_date_local_time_zone (ecma_number_t time) /**< time value */
 {
-  jerry_time_zone_t tz;
-
-  if (ecma_number_is_nan (time)
-      || !jerry_port_get_time_zone (&tz))
-  {
-    return ecma_number_make_nan ();
-  }
-
-  return ecma_date_local_tza (&tz) + ecma_date_daylight_saving_ta (&tz, time);
+  return jerry_port_get_local_tza (time, true);
 } /* ecma_date_local_time_zone */
 
 /**
@@ -369,16 +326,7 @@ ecma_date_local_time_zone (ecma_number_t time) /**< time value */
 ecma_number_t
 ecma_date_utc (ecma_number_t time) /**< time value */
 {
-  jerry_time_zone_t tz;
-
-  if (ecma_number_is_nan (time)
-      || !jerry_port_get_time_zone (&tz))
-  {
-    return ecma_number_make_nan ();
-  }
-
-  ecma_number_t simple_utc_time = time - ecma_date_local_tza (&tz);
-  return simple_utc_time - ecma_date_daylight_saving_ta (&tz, simple_utc_time);
+  return time - jerry_port_get_local_tza (time, false);
 } /* ecma_date_utc */
 
 /**
diff --git a/jerry-core/include/jerryscript-port.h b/jerry-core/include/jerryscript-port.h
index 59e4b61d29..6263cc114c 100644
--- a/jerry-core/include/jerryscript-port.h
+++ b/jerry-core/include/jerryscript-port.h
@@ -111,27 +111,19 @@ void JERRY_ATTR_FORMAT (printf, 2, 3) jerry_port_log (jerry_log_level_t level, c
  */
 
 /**
- * Jerry time zone structure
- */
-typedef struct
-{
-  int offset;                /**< minutes from west */
-  int daylight_saving_time;  /**< daylight saving time (1 - DST applies, 0 - not on DST) */
-} jerry_time_zone_t;
-
-/**
- * Get timezone and daylight saving data
+ * Get local timezone adjustment, in milliseconds. This value, added to a timestamp in UTC
+ * time, should yield local time. Ideally, this function should satisfy the stipulations
+ * applied to LocalTZA in section 20.3.1.7 of ecmascript version 9.0 [1].
+ * [1] https://www.ecma-international.org/ecma-262/9.0/#sec-local-time-zone-adjustment
  *
  * Note:
  *      This port function is called by jerry-core when
- *      CONFIG_DISABLE_DATE_BUILTIN is _not_ defined. Otherwise this function is
- *      not used.
+ *      CONFIG_DISABLE_DATE_BUILTIN is _not_ defined. Otherwise this function
+ *      is not used.
  *
- * @param[out] tz_p time zone structure to fill.
- * @return true  - if success
- *         false - otherwise
+ * @return milliseconds between local time and utc for the given timestamp.
  */
-bool jerry_port_get_time_zone (jerry_time_zone_t *tz_p);
+double jerry_port_get_local_tza (double js_time_ms, bool is_utc);
 
 /**
  * Get system time
diff --git a/jerry-port/default/CMakeLists.txt b/jerry-port/default/CMakeLists.txt
index e388dc9936..025965a24d 100644
--- a/jerry-port/default/CMakeLists.txt
+++ b/jerry-port/default/CMakeLists.txt
@@ -26,6 +26,12 @@ file(GLOB SOURCE_PORT_DEFAULT *.c)
 # (should only be necessary if we used compiler default libc but not checking that)
 set(DEFINES_PORT_DEFAULT _BSD_SOURCE _DEFAULT_SOURCE)
 
+INCLUDE (CheckStructHasMember)
+CHECK_STRUCT_HAS_MEMBER ("struct tm" tm_gmtoff time.h HAVE_TM_GMTOFF)
+if(HAVE_TM_GMTOFF)
+  set(DEFINES_PORT_DEFAULT ${DEFINES_PORT_DEFAULT} HAVE_TM_GMTOFF)
+endif()
+
 # Sleep function availability check
 INCLUDE (CheckIncludeFiles)
 CHECK_INCLUDE_FILES (time.h HAVE_TIME_H)
diff --git a/jerry-port/default/default-date.c b/jerry-port/default/default-date.c
index 837ef7d80e..6eca404af9 100644
--- a/jerry-port/default/default-date.c
+++ b/jerry-port/default/default-date.c
@@ -13,6 +13,9 @@
  * limitations under the License.
  */
 
+#ifdef HAVE_TM_GMTOFF
+#include <time.h>
+#endif
 #ifdef __GNUC__
 #include <sys/time.h>
 #endif
@@ -21,33 +24,32 @@
 #include "jerryscript-port-default.h"
 
 /**
- * Default implementation of jerry_port_get_time_zone. Uses 'gettimeofday' if
- * available on the system, does nothing otherwise.
+ * Default implementation of jerry_port_get_local_tza. Uses the `tm_gmtoff` field
+ * of `struct tm` (a GNU extension) filled by `localtime_r` if available on the
+ * system, does nothing otherwise.
  *
- * @return true - if 'gettimeofday' is available and executed successfully,
- *         false - otherwise.
+ * @return offset between utc and localtime at the given unix timestamp, if
+ *         available. 0 otherwise.
  */
-bool jerry_port_get_time_zone (jerry_time_zone_t *tz_p) /**< [out] time zone structure to fill */
+double jerry_port_get_local_tza (double unix_ms,  /**< ms since unix epoch */
+                                 bool is_utc)  /**< is the time above in utc? */
 {
-#ifdef __GNUC__
-  struct timeval tv;
-  struct timezone tz;
-
-  /* gettimeofday may not fill tz, so zero-initializing */
-  tz.tz_minuteswest = 0;
-  tz.tz_dsttime = 0;
-
-  if (gettimeofday (&tv, &tz) == 0)
+#ifdef HAVE_TM_GMTOFF
+  struct tm tm;
+  time_t now = (time_t)(unix_ms / 1000);
+  localtime_r (&now, &tm);
+  if (!is_utc)
   {
-    tz_p->offset = tz.tz_minuteswest;
-    tz_p->daylight_saving_time = tz.tz_dsttime > 0 ? 1 : 0;
-
-    return true;
+    now -= tm.tm_gmtoff;
+    localtime_r (&now, &tm);
   }
-#endif /* __GNUC__ */
-
-  return false;
-} /* jerry_port_get_time_zone */
+  return ((double) tm.tm_gmtoff) * 1000;
+#else
+  (void) unix_ms;
+  (void) is_utc;
+  return 0.0;
+#endif /* HAVE_TM_GMTOFF */
+} /* jerry_port_get_local_tza */
 
 /**
  * Default implementation of jerry_port_get_current_time. Uses 'gettimeofday' if
diff --git a/targets/curie_bsp/source/curie-bsp-port.c b/targets/curie_bsp/source/curie-bsp-port.c
index 97cb896c42..b92643be22 100644
--- a/targets/curie_bsp/source/curie-bsp-port.c
+++ b/targets/curie_bsp/source/curie-bsp-port.c
@@ -52,16 +52,13 @@ void jerry_port_fatal (jerry_fatal_code_t code)
 } /* jerry_port_fatal */
 
 /**
- * Curie BSP implementation of jerry_port_get_time_zone.
+ * Curie BSP implementation of jerry_port_get_local_tza.
  */
-bool jerry_port_get_time_zone (jerry_time_zone_t *tz_p)
+double jerry_port_get_local_tza (double js_time_ms, bool is_utc)
 {
   //EMPTY implementation
-  tz_p->offset = 0;
-  tz_p->daylight_saving_time = 0;
-
-  return true;
-} /* jerry_port_get_time_zone */
+  return 0;
+} /* jerry_port_get_local_tza */
 
 /**
  * Curie BSP implementation of jerry_port_get_current_time.
diff --git a/targets/esp8266/user/jerry_port.c b/targets/esp8266/user/jerry_port.c
index 7ba25e43ad..725b05662a 100644
--- a/targets/esp8266/user/jerry_port.c
+++ b/targets/esp8266/user/jerry_port.c
@@ -63,14 +63,11 @@ jerry_port_get_current_time (void)
 /**
  * Dummy function to get the time zone.
  *
- * @return true
+ * @return 0, no time zone.
  */
-bool
-jerry_port_get_time_zone (jerry_time_zone_t *tz_p)
+double
+jerry_port_get_local_tza (double js_time_ms, bool is_utc)
 {
   /* We live in UTC. */
-  tz_p->offset = 0;
-  tz_p->daylight_saving_time = 0;
-
-  return true;
-} /* jerry_port_get_time_zone */
+  return 0;
+} /* jerry_port_get_local_tza */
diff --git a/targets/mbedos5/source/jerry_port_mbed.c b/targets/mbedos5/source/jerry_port_mbed.c
index 3e225b0136..182a08cf32 100644
--- a/targets/mbedos5/source/jerry_port_mbed.c
+++ b/targets/mbedos5/source/jerry_port_mbed.c
@@ -46,17 +46,15 @@ jerry_port_log (jerry_log_level_t level, /**< log level */
 #endif /* JSMBED_OVERRIDE_JERRY_PORT_LOG */
 
 /**
- * Implementation of jerry_port_get_time_zone.
+ * Implementation of jerry_port_get_local_tza.
  *
- * @return true - if success
+ * @return 0, as we live in UTC.
  */
-bool
-jerry_port_get_time_zone (jerry_time_zone_t *tz_p) /**< timezone pointer */
+double
+jerry_port_get_local_tza (double js_time_ms, bool is_utc)
 {
-  tz_p->offset = 0;
-  tz_p->daylight_saving_time = 0;
-  return true;
-} /* jerry_port_get_time_zone */
+  return 0;
+} /* jerry_port_get_local_tza */
 
 /**
  * Implementation of jerry_port_get_current_time.
diff --git a/targets/nuttx-stm32f4/jerry_main.c b/targets/nuttx-stm32f4/jerry_main.c
index ef6a63c798..da7e10f470 100644
--- a/targets/nuttx-stm32f4/jerry_main.c
+++ b/targets/nuttx-stm32f4/jerry_main.c
@@ -492,19 +492,16 @@ jerry_port_log (jerry_log_level_t level, /**< log level */
 } /* jerry_port_log */
 
 /**
- * Dummy function to get the time zone.
+ * Dummy function to get the time zone adjustment.
  *
- * @return true
+ * @return 0
  */
-bool
-jerry_port_get_time_zone (jerry_time_zone_t *tz_p)
+double
+jerry_port_get_local_tza (double js_time_ms, bool is_utc)
 {
   /* We live in UTC. */
-  tz_p->offset = 0;
-  tz_p->daylight_saving_time = 0;
-
-  return true;
-} /* jerry_port_get_time_zone */
+  return 0;
+} /* jerry_port_get_local_tza */
 
 /**
  * Dummy function to get the current time.
diff --git a/targets/tizenrt-artik053/apps/jerryscript/jerry_main.c b/targets/tizenrt-artik053/apps/jerryscript/jerry_main.c
index ce8cbe23ae..54d966b492 100644
--- a/targets/tizenrt-artik053/apps/jerryscript/jerry_main.c
+++ b/targets/tizenrt-artik053/apps/jerryscript/jerry_main.c
@@ -474,19 +474,16 @@ jerry_port_log (jerry_log_level_t level, /**< log level */
 } /* jerry_port_log */
 
 /**
- * Dummy function to get the time zone.
+ * Dummy function to get the time zone adjustment.
  *
- * @return true
+ * @return 0
  */
-bool
-jerry_port_get_time_zone (jerry_time_zone_t *tz_p)
+double
+jerry_port_get_local_tza (double js_time_ms, bool is_utc)
 {
   /* We live in UTC. */
-  tz_p->offset = 0;
-  tz_p->daylight_saving_time = 0;
-
-  return true;
-} /* jerry_port_get_time_zone */
+  return 0;
+} /* jerry_port_get_local_tza */
 
 /**
  * Dummy function to get the current time.
diff --git a/targets/zephyr/src/jerry-port.c b/targets/zephyr/src/jerry-port.c
index b1eb9dcb67..9d05d2699e 100644
--- a/targets/zephyr/src/jerry-port.c
+++ b/targets/zephyr/src/jerry-port.c
@@ -59,19 +59,16 @@ jerry_port_get_current_time (void)
 } /* jerry_port_get_current_time */
 
 /**
- * Dummy function to get the time zone.
+ * Dummy function to get the time zone adjustment.
  *
- * @return true
+ * @return 0
  */
-bool
-jerry_port_get_time_zone (jerry_time_zone_t *tz_p)
+double
+jerry_port_get_local_tza (double js_time_ms, bool is_utc)
 {
   /* We live in UTC. */
-  tz_p->offset = 0;
-  tz_p->daylight_saving_time = 0;
-
-  return true;
-} /* jerry_port_get_time_zone */
+  return 0;
+} /* jerry_port_get_local_tza */
 
 /**
  * Provide the implementation of jerryx_port_handler_print_char.