rng = pd.date_range('3/6/2012 00:00', periods=2, freq='D')
ts = pd.Series(np.random.randn(len(rng)), rng)

ts_utc = ts.tz_localize('UTC')

返回 ts_utc:

2012-03-06 00:00:00+00:00    0.464000
2012-03-07 00:00:00+00:00    0.227371