A minimum 19 year tidal prediction dataset covering nodal (satellite) modulation effects is required to determine the Lowest Astronomical Tide (LAT) and Highest Astronomical Tide (HAT) datums. In this study, we explore the ability of a widely used conventional standard harmonic prediction program, T_TIDE ‘t_predic.m’ from Pawlowicz et al. (2002), to produce accurate continuous multi-year predictions. Comparisons are made with the more recent tidal prediction program, UTide ‘ut_reconstr.m’ from Codiga (2011). Tidal height records for two different regimes are employed: for diurnal tides data are employed from Cape Roberts in Antarctica, while for semi-diurnal tides data are used from Incheon, Gyeonggi Bay, Korea. Results demonstrate an issue arises in continuous multi-year tidal predictions made via T_TIDE, due to the program’s single calculation (fixed) of nodal modulation corrections (NMC). We explain a modified NMC update method that successfully solves this problem, rendering the program of use for accurate continuous multi-year tidal predictions.