review doc

docs/using/methods.rst

@@ -42,12 +42,12 @@ metadata()
 provenance()
    Return the dataset's provenance information.
 
-source(index):
+source(index)
    For debugging. Given the index of variable, this will return from
    which Zarr store it will be loaded. This is useful to debug combining
    datasets with :ref:`join`.
 
-tree():
+tree()
    For debugging. Return the dataset's internal tree structure.
 
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docs/using/subsetting.rst

@@ -14,6 +14,7 @@ Subsetting is the action of filtering the dataset by its first dimension
 *******
 
 This option let you subset the dataset by time. You can pass a date or a
+string:
 
 .. literalinclude:: code/start_.py
 
@@ -34,6 +35,15 @@ The following are equivalent way of describing ``start`` or ``end``:
 -  ``202306``, ``"202306"`` and ``"2023-06"``
 -  ``20200301``, ``"20200301"`` and ``"2020-03-01"``
 
+Note that the ``start="2020"`` is equivalent to ``start="2020-01-01"``
+while ``end="2020"`` is equivalent to ``end="2020-12-31"``.
+
+Note also how the ``frequency`` of the dataset will change how the
+``end`` option is interpreted: - ``end="2020"`` with a ``frequency`` of
+one hour is equivalent to ``end="2020-12-31 23:00"`` - ``end="2020"``
+with a ``frequency`` of 6 hours is equivalent to ``end="2020-12-31
+18:00"``
+
 .. _frequency:
 
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