diff --git a/docs/05.PORT-API.md b/docs/05.PORT-API.md
index c5cb98f4d..9a7cd82b4 100644
--- a/docs/05.PORT-API.md
+++ b/docs/05.PORT-API.md
@@ -11,7 +11,8 @@ It is questionable whether a library should be able to terminate an application.
  *
  * @param code gives the cause of the error.
  *
- * Note: jerry expects the function not to return.
+ * Note:
+ *      Jerry expects the function not to return.
  *
  * Example: a libc-based port may implement this with exit() or abort(), or both.
  */
@@ -81,14 +82,25 @@ typedef struct
 /**
  * Get timezone and daylight saving data
  *
+ * Note:
+ *      This port function is called by jerry-core when
+ *      CONFIG_DISABLE_DATE_BUILTIN is _not_ defined. Otherwise this function is
+ *      not used.
+ *
  * @return true  - if success
  *         false - otherwise
  */
-bool jerry_port_get_time_zone (jerry_time_zone_t *);
+bool jerry_port_get_time_zone (jerry_time_zone_t *tz_p);
 
 /**
  * Get system time
  *
+ * Note:
+ *      This port function is called by jerry-core when
+ *      CONFIG_DISABLE_DATE_BUILTIN is _not_ defined. It is also common practice
+ *      in application code to use this function for the initialization of the
+ *      random number generator.
+ *
  * @return milliseconds since Unix epoch
  */
 double jerry_port_get_current_time (void);
@@ -100,12 +112,13 @@ Allow user to provide external buffer for jerry instance (which includes an isol
 
 ```c
 /**
- * Get the current instance, which contains the current context, heap and other infomation.
- * Each port should provide its own implementation of this interface.
+ * Get the current instance which contains the current context, heap and other
+ * structures. Each port should provide its own implementation of this interface.
  *
- *Note:
- *    This port function will be called automatically by jerry-core
- *    when JERRY_ENABLE_EXTERNAL_CONTEXT is defined. If not, this function will never be called.
+ * Note:
+ *      This port function is called by jerry-core when
+ *      JERRY_ENABLE_EXTERNAL_CONTEXT is defined. Otherwise this function is not
+ *      used.
  *
  * @return the pointer to the jerry instance.
  */
@@ -117,6 +130,10 @@ struct jerry_instance_t *jerry_port_get_current_instance (void);
 ```c
 /**
  * Makes the process sleep for a given time.
+ *
+ * Note:
+ *      This port function is called by jerry-core when JERRY_DEBUGGER is
+ *      defined. Otherwise this function is not used.
  */
 void jerry_port_sleep (uint32_t sleep_time);
 ```
diff --git a/jerry-core/include/jerryscript-port.h b/jerry-core/include/jerryscript-port.h
index 95a976343..8fc8ba882 100644
--- a/jerry-core/include/jerryscript-port.h
+++ b/jerry-core/include/jerryscript-port.h
@@ -114,6 +114,11 @@ typedef struct
 /**
  * Get timezone and daylight saving data
  *
+ * Note:
+ *      This port function is called by jerry-core when
+ *      CONFIG_DISABLE_DATE_BUILTIN is _not_ defined. Otherwise this function is
+ *      not used.
+ *
  * @return true  - if success
  *         false - otherwise
  */
@@ -122,6 +127,12 @@ bool jerry_port_get_time_zone (jerry_time_zone_t *tz_p);
 /**
  * Get system time
  *
+ * Note:
+ *      This port function is called by jerry-core when
+ *      CONFIG_DISABLE_DATE_BUILTIN is _not_ defined. It is also common practice
+ *      in application code to use this function for the initialization of the
+ *      random number generator.
+ *
  * @return milliseconds since Unix epoch
  */
 double jerry_port_get_current_time (void);
@@ -130,9 +141,10 @@ double jerry_port_get_current_time (void);
  * Get the current instance which contains the current context, heap and other
  * structures. Each port should provide its own implementation of this interface.
  *
- *Note:
- *    This port function is called by jerry-core when JERRY_ENABLE_EXTERNAL_CONTEXT
- *    is defined. Otherwise this function is not used.
+ * Note:
+ *      This port function is called by jerry-core when
+ *      JERRY_ENABLE_EXTERNAL_CONTEXT is defined. Otherwise this function is not
+ *      used.
  *
  * @return the pointer to the jerry instance.
  */
@@ -140,10 +152,12 @@ struct jerry_instance_t *jerry_port_get_current_instance (void);
 
 /**
  * Makes the process sleep for a given time.
+ *
+ * Note:
+ *      This port function is called by jerry-core when JERRY_DEBUGGER is
+ *      defined. Otherwise this function is not used.
  */
-#ifdef JERRY_DEBUGGER
 void jerry_port_sleep (uint32_t sleep_time);
-#endif /* JERRY_DEBUGGER */
 
 /**
  * @}