Is your feature request related to a problem?

As a pandas user, I wish I could use pandas to determine which values in a DatetimeIndex are using DST (Daylight Saving Time). This could be useful for a datetime column that recorded values year-round (ex - 1 column with EDT and EST datetimes).

Describe the solution you'd like

  • An attribute on DatetimeIndex that is named is_daylight_savings_time or is_dst)

API breaking implications

  • None, this is an additive feature

Additional context

  • This issue resulted from this discussion:
  • https://github.com/pandas-dev/pandas/issues/46998#issuecomment-1135083658
  • This attribute could return the following (for each datetime value):
  • Value is 0 when DST is not in effect.
  • Value is 1 when DST is in effect.
  • Value is -1 when DST is unknown.

Comment From: mroeschke

I tried implementing this a few years ago, and it was discouraged https://github.com/pandas-dev/pandas/pull/22560#issuecomment-418707870= so I am not sure it's likely that this will be implemented

Comment From: jreback

idk i think this could be useful (or we add fold instead maybe is better)

Comment From: jbrockmendel

Following #49684, an easy (but non-performant) way to implement this will be folds = np.array([x.fold for x in self], dtype=bool). For a more performant implementation we'd need to refactor out parts of ints_to_pydatetime.