1. Radio pulsar timing --- 0.1 microseconds over years
2. Astronomical X-ray data --- 0.01 microseconds over years
3. Planet Ephemerides --- 1 microseconds over decades
4. Laser/Atomic Spectroscopy --- 0.1 femtoseconds over milliseconds
5. Fusion --- 1 nanoseconds over seconds
6. Neutrino detection --- 1 millisecond over decades
=Fred Knight (INTERNET:knight@ll.mit.edu)