2025RAA....25a5013W

Determining accurate pulsar timing model parameters is essential for establishing TT(PT), a realization of Terrestrial Time (TT) based on a pulsar timescale (PT). This study discusses the impact of different data spans on the accuracy of pulsar timing model parameters when determining pulsar timing model parameters. Using observations of PSR J0437-4715, J1909-3744, J1713+0747, and J1744-1134 from the second data release of the International Pulsar Timing Array (IPTA II, Version A), we compare the accuracy of the timing model parameters determined by these observations with different data spans. The results show for PSR J0437-4715, J1713+0747, and J1909-3744, the amplitude fluctuations of rotational frequency remain within 10^–15, 10^–14, and 10^–14 Hz, respectively, when the data spans for determining pulsar timing model parameters exceed 13, 14, and 6 yr. Additionally, the one-year accuracy of TT(PT) is crucial for its application in timekeeping. By comparing the frequency deviations of TT(PT) relative to TT(BIPM) under both ideal (k_r) and actual (k_p) conditions across different data spans, we find that when the data span reaches the duration above, the accuracy of TT(PT) surpasses that of TT(TAI) under ideal conditions, slightly inferior under actual conditions. This suggests with improved observational technologies, the accuracy of TT(PT) can be further enhanced.