  We report a measurement of the absolute frequency of the 1S0-3P0 transition
in the 171Yb optical lattice clock at KRISS (KRISS-Yb1) for 14 months, which
was referenced to the SI second by primary and secondary standards worldwide
via TAI (International Atomic Time). The determined absolute frequency is 518
295 836 590 863.75(14) Hz with the relative frequency uncertainty of
2.6x10^-16, which agrees well with other reports. This result is expected to
contribute to the future update of the CIPM recommendation frequency of the
secondary frequency standards.

Atomic Physics