data = """col1                 col2
02:10:00.008209    02:08:38.053145
02:10:00.567054    02:08:38.053145
02:10:00.609842    02:08:38.053145
02:10:00.728153    02:08:38.053145
02:10:02.394408    02:08:38.053145"""
df = pd.read_table(io.BytesIO(data), delim_whitespace=True)
df2 = df.apply(pd.to_timedelta)
diff = df2.col1 - df2.col2
diff.astype('i8') / 1000000000.0
python pandas datetime.time - datetime.time