df = pd.DataFrame({'Date': ['2014-01-14', '2014-01-14', '2014-01-14',
    '2014-01-14', '2014-05-12', '2014-05-12'], 'Time': ['12:00:04',
    '12:01:12', '12:01:19', '12:05:49', '01:01:59', '1:02:42'], 'value': [
    0.424, 0.342, 0.341, 0.23, 0.0, 0.23]})
df['Date'] = pd.to_datetime(df['Date'])
df['Time'] = pd.to_timedelta(df['Time'])
df = df.set_index(['Date', 'Time'])
df = df.reset_index()
idx = df.groupby(['Date'])['Time'].idxmax()
print(df.loc[idx])
Multi-indexing - accessing the last time in every day