Flag Daylight Saving Time (DST) Hours in Pandas Date-Time Column

Question

I created an hourly dates dataframe, and now I would like to create a column that flags whether each row (hour) is in Daylight Saving Time or not. For example, in summer hou

Answer 1

Here is what I ended up doing, and it works for my purposes:

import pandas as pd
import pytz

# Create dates table and flag Daylight Saving Time dates
dates = pd.DataFrame(data=pd.date_range('2018-1-1', '2018-12-31-23', freq='h'), columns=['date_time'])

# Create a list of start and end dates for DST in each year, in UTC time
dst_changes_utc = pytz.timezone('America/Denver')._utc_transition_times[1:]

# Convert to local times from UTC times and then remove timezone information
dst_changes = [pd.Timestamp(i).tz_localize('UTC').tz_convert('America/Denver').tz_localize(None) for i in dst_changes_utc]

flag_list = []
for index, row in dates['date_time'].iteritems():
    # Isolate the start and end dates for DST in each year
    dst_dates_in_year = [date for date in dst_changes if date.year == row.year]
    spring = dst_dates_in_year[0]
    fall = dst_dates_in_year[1]
    if (row >= spring) & (row < fall):
        flag = 1
    else:
        flag = 0
    flag_list.append(flag)
print(flag_list)
dates['dst_flag'] = flag_list
del(flag_list)