Update description and examples of the datetime object methods

Part of #2411

Author: veod32

doc/reference/reference_lua/datetime.rst

@@ -4,9 +4,9 @@ Module datetime
 
 Since :doc:`2.10.0 </release/2.10.0>`.
 
-The ``datetime`` module provides support of the timestamp and interval data types. [TDB -- links].
-It allows to create the date and timestamp values using either object interface,
-or via parsing the string values conforming to ISO-8601 standard.
+The ``datetime`` module provides support for the :ref:`datetime and interval data types <index-box_datetime>`.
+It allows creating the date and time values either via the object interface
+or via parsing string values conforming to the ISO-8601 standard.
 
 Below is a list of the ``datetime`` module functions and methods.
 
@@ -23,16 +23,16 @@ Below is a list of the ``datetime`` module functions and methods.
             -   Use
 
         *   -   :doc:`./datetime/new`
-            -   Create a datetime object from a table of date and time values/parameters
+            -   Create a ``datetime`` object from a table of time units
 
         *   -   :ref:`format() <datetime-format>`
-            -   Convert a datetime object into a string of a particular format
+            -   Convert the standard presentation of a ``datetime`` object into a formatted string
 
         *   -   :ref:`totable() <datetime-totable>`
-            -   Convert a datetime object into a Lua table
+            -   Convert the information from a ``datetime`` object into the table format
 
         *   -   :ref:`set() <datetime-set>`
-            -   Update the field values in the existing datetime object
+            -   Update the field values in the existing ``datetime`` object
 
 
 

doc/reference/reference_lua/datetime/datetime_object.rst

@@ -56,7 +56,7 @@ datetime_object
                 *   -   tzoffset
                     -   Time zone offset from UTC
 
-        :return: table with the date and time parameters [TBD]
+        :return: table with the date and time parameters [TBD - description]
         :rtype: table
 
         **Example:**
@@ -95,12 +95,13 @@ datetime_object
     ..  method:: format( ['convension_specifications'] )
 
         Convert the standard ``datetime`` object presentation into a formatted string.
-        The convension specifications are the same as in the `FreeBSD strftime <https://www.freebsd.org/cgi/man.cgi?query=strftime&sektion=3>`__.
-        Additional convension for nanoseconds is `%f` which also allows the modifier to control the output precision of fractional part (see example below).
+        The formatting convension specifications are the same as in the `FreeBSD strftime <https://www.freebsd.org/cgi/man.cgi?query=strftime&sektion=3>`__.
+        Additional convension for nanoseconds is `%f` which also allows a modifier to control the output precision of fractional part: `%5f` (see the example below).
+        If no arguments are set for the method, the default convensions are used: `'%FT%T.%f%z'` (see the example below).
 
-        :param string convension_specifications: [TBD]
+        :param string convension_specifications: string consisting of zero or more conversion specifications and ordinary characters
 
-        :return: string with the formatted date and time information [TBD]
+        :return: string with the formatted date and time information
         :rtype: string
 
         **Example:**
@@ -128,6 +129,16 @@ datetime_object
             - 20.08.21 18:25:20.12345
             ...
 
+            tarantool> dt:format()
+            ---
+            - 2021-08-20T18:25:20.123456789+0300
+            ...
+
+            tarantool> dt:format('%FT%T.%f%z')
+            ---
+            - 2021-08-20T18:25:20.123456789+0300
+            ...
+
     ..  _datetime-set:
 
     ..  method:: set( [{ time_units }] )
@@ -165,4 +176,4 @@ datetime_object
             tarantool> dt:set {tzoffset = 60}
             ---
             - 2021-08-20T18:25:20.567+0100
-...
+            ...