Indicate whether the date is the first day of a year.


The same type as the original data with boolean values. Series will have the same name and index. DatetimeIndex will have the same name.

Return type

Series or DatetimeIndex

See also


Similar property indicating the last day of the year.


This method is available on Series with datetime values under the .dt accessor, and directly on DatetimeIndex.

>>> dates = pd.Series(pd.date_range("2017-12-30", periods=3))  
>>> dates  
0   2017-12-30
1   2017-12-31
2   2018-01-01
dtype: datetime64[ns]
>>> dates.dt.is_year_start  
0    False
1    False
2    True
dtype: bool
>>> idx = pd.date_range("2017-12-30", periods=3)  
>>> idx  
DatetimeIndex(['2017-12-30', '2017-12-31', '2018-01-01'],
              dtype='datetime64[ns]', freq='D')
>>> idx.is_year_start  
array([False, False,  True])

This docstring was copied from pandas.core.indexes.accessors.CombinedDatetimelikeProperties.