DOCSP-8897: [Charts] Smart labels for dates (#308)

Author: steveren

source/customize-charts/value-axis-options.txt

@@ -47,11 +47,12 @@ allowing the viewer to focus on more relevant information.
    of zero is not recommended. Doing so means the length of the
    bars is no longer proportional to the data point values.
 
-Available for the following chart types: all :ref:`Bar/Column
-<column-bar-chart-ref>` except 100% stacked,
-:ref:`Discrete and Continuous Line
-<line-area-chart-ref>`, :ref:`Discrete and Continuous Area
-<discrete-charts>`, :ref:`Scatter <scatter-chart-ref>`
+The following chart types can use max and min: 
+
+- all :ref:`Bar/Column <column-bar-chart-ref>` except 100% stacked
+- :ref:`Discrete and Continuous Line <line-area-chart-ref>`
+- :ref:`Discrete and Continuous Area <discrete-charts>`
+- :ref:`Scatter <scatter-chart-ref>`
 
 Logarithmic Scale
 -----------------
@@ -82,10 +83,11 @@ Logarithmic Scale Considerations
   a value greater than zero but smaller than the lowest value in the
   data set.
 
-Available for the following chart types: :ref:`Grouped and
-Colored Bar/Column <column-bar-chart-ref>`, :ref:`Discrete and
-Continuous Line <line-area-chart-ref>`, :ref:`Scatter
-<scatter-chart-ref>`
+The following chart types can use logarithmic scale: 
+
+- :ref:`Grouped and Colored Bar/Column <column-bar-chart-ref>`
+- :ref:`Discrete and Continuous Line <line-area-chart-ref>`
+- :ref:`Scatter <scatter-chart-ref>`
 
 Label Override
 --------------
@@ -102,6 +104,42 @@ To customize the axis label for charts that have a single field mapped,
 use the Label Override option within that field's customization
 options.
 
-Available for the following chart types: :ref:`Bar/Column
-<column-bar-chart-ref>`, :ref:`Line <line-area-chart-ref>`,
-:ref:`Area <line-area-chart-ref>`, :ref:`Scatter <scatter-chart-ref>`
+The following chart types can use label override:
+
+- :ref:`Bar/Column <column-bar-chart-ref>`
+- :ref:`Line <line-area-chart-ref>`
+- :ref:`Area <line-area-chart-ref>`
+- :ref:`Scatter <scatter-chart-ref>`
+
+Smart Labels for Dates
+----------------------
+
+Smart labels for dates are axis markers grouped by units of time to reduce
+repetition of information. They are generated automatically based on the range of
+the chart when a ``date`` type field is encoded on an ``X`` or ``Y`` value axis. 
+
+The following chart types can use smart labels for dates:
+
+- :ref:`Continuous Line and Area Charts <continuous-charts>`
+- :ref:`Scatter Charts <scatter-chart-ref>`
+
+Smart labels are enabled by default when dates fields are encoded on value
+axes on supported chart types.. To toggle smart labels on and off:
+
+1. Click the :guilabel:`Customize` tab above the :ref:`encoding channels
+   <encoding-channels>` in the :doc:`Chart Builder </build-charts>`.
+
+#. Click the :guilabel:`X` or :guilabel:`Y Axis` section.
+
+#. If the :guilabel:`Use Smart Labels on Axis` toggle swich is set
+   to :guilabel:`Off`, toggle it to :guilabel:`On`.
+
+.. figure:: /images/charts/smart-label-switch.png
+   :figwidth: 220px
+   :alt: Smart label toggle switch
+
+.. note::
+
+   When smart labels are enabled, date and time formatting options remain
+   available. Any formatting options you apply are visible in the chart's
+   tooltips.