DataFrame combine_first() loses timezone information for datetime columns · Issue #10567 · pandas-dev/pandas (original) (raw)

dts1 = pd.date_range('20150101','20150105',tz='UTC')
df1 = pd.DataFrame({'DATE':dts1})
dts2 = pd.date_range('20150103','20150105',tz='UTC')
df2 = pd.DataFrame({'DATE':dts2})
df = df1.combine_first(df2)
df.DATE[0].tz # this shows up as None