Add basic datetime functionality (#275)

* add datetime accessor

* remove floor

* fixup

* remove .dt accessor, specify integerness of return columns

* fixup

* ci

Author: MarcoGorelli

spec/API_specification/dataframe_api/column_object.py

@@ -819,3 +819,85 @@ def rename(self, name: str) -> Self:
             New column - this does not operate in-place.
         """
         ...
+
+
+    def year(self) -> Self:
+        """
+        Return 'year' component of each element of `Date` and `Datetime` columns.
+        
+        For example, return 1981 for 1981-01-02T12:34:56.123456.
+
+        Return column should be of (signed) integer dtype.
+        """
+        ...
+
+    def month(self) -> Self:
+        """
+        Return 'month' component of each element of `Date` and `Datetime` columns.
+        
+        For example, return 1 for 1981-01-02T12:34:56.123456.
+
+        Return column should be of integer dtype (signed or unsigned).
+        """
+        ...
+
+    def day(self) -> Self:
+        """
+        Return 'day' component of each element of `Date` and `Datetime` columns.
+        
+        For example, return 2 for 1981-01-02T12:34:56.123456.
+
+        Return column should be of integer dtype (signed or unsigned).
+        """
+        ...
+
+    def hour(self) -> Self:
+        """
+        Return 'hour' component of each element of `Date` and `Datetime` columns.
+        
+        For example, return 12 for 1981-01-02T12:34:56.123456.
+
+        Return column should be of integer dtype (signed or unsigned).
+        """
+        ...
+
+    def minute(self) -> Self:
+        """
+        Return 'minute' component of each element of `Date` and `Datetime` columns.
+        
+        For example, return 34 for 1981-01-02T12:34:56.123456.
+
+        Return column should be of integer dtype (signed or unsigned).
+        """
+        ...
+
+    def second(self) -> Self:
+        """
+        Return 'second' component of each element of `Date` and `Datetime` columns.
+        
+        For example, return 56 for 1981-01-02T12:34:56.123456.
+
+        Return column should be of integer dtype (signed or unsigned).
+        """
+        ...
+
+    def microsecond(self) -> Self:
+        """
+        Return number of microseconds since last second, for each element of `Date` and `Datetime` columns.
+
+        For example, return 123456 for 1981-01-02T12:34:56.123456.
+
+        Return column should be of integer dtype (signed or unsigned).
+        """
+        ...
+    
+    def iso_weekday(self) -> Self:
+        """
+        Return ISO weekday for each element of `Date` and `Datetime` columns.
+
+        Note that Monday=1, ..., Sunday=7.
+
+        Return column should be of integer dtype (signed or unsigned).
+        """
+        ...
+