We have developed two all-optical clocks in which the RF output is generated directly from the optical process within the clockwork. The frequency comb created by a femtosecond mode-locked laser and a microstructure fiber is used to phase-coherently measure the frequencies of both the Hg/sup +/ and Ca optical frequency standards with respect to the SI second as realized at NIST. We find the transition frequencies to bef/sub Hg/=1064721609899143(10) Hz and f/sub Ca/ =455986240494158(26) Hz, respectively. This work begins to reveal the high stability and potential for accuracy of optical atomic clocks. Furthermore, when combined with previous measurements, we find no time variations of these atomic frequencies within the uncertainties of 1|(/spl part/f/sub Hg///spl part/t)/f/sub Hg/| =2/spl times/10/sup -14/ yr/sup -1/ and |(/spl part/f/sub Ca///spl part/t)/f/sub Ca/| =8/spl times/10/sup -14/ yr/sup -1/.