We study the short-time dynamics of systems that develop quasi-long-range order after a quench to the Kosterlitz-Thouless phase. With the working hypothesis that the universal short-time behavior, previously found in Ising-like systems, also occurs in the Kosterlitz-Thouless phase, we explore the scaling behavior of thermodynamic variables during the relaxational process following the quench. As a concrete example, we investigate the two-dimensional six-state clock model by Monte Carlo simulation. The exponents governing the magnetization, the second moment, and the autocorrelation function are calculated. From them, by means of scaling relations, estimates for the equilibrium exponents z and eta are derived. In particular, our estimates for the temperature-dependent anomalous dimension eta that governs the static correlation function are consistent with existing analytical and numerical results, and, thus, confirm our working hypothesis.