We reviewed the research progress on time keeping metrology using millisecond pulsars. Millisecond pulsars exhibit a very stable spinning period, so that their rotational phase may be used as a time reference, named pulsar time (PT) . The analyses of high precision timing data for two millisecond pulsars showed that the long-term stability of TA-PT may be compared to atomic time TA. It is possible that an average pulsar time scale PT_ens may be deduced through a long-term stability algorithm using precision timing data from more millisecond pulsars. Such an ensemble average can reduce the level of the instabilities originating from individual pulsar and other sources of noise. By comparison between ensemble pulsar time and terrestrial atomic time, one will get some insight on long term stability of atomic time. The orbital motion of close binary pulsar can be used for generation of an astronomical ephemeris time scale BPT. An introduction on the definition of binary pulsar time BPT was given.