Phasor Measurement Units (PMUs) provide time synchronized electrical measurements at many nodes across the power grid. This wide area time synchronization is made possible via GPS time transfer. Unfortunately, the GPS civilian signal is weak and vulnerable to signal interferences such as jamming and meaconing. As such, the GPS-based time synchronization of PMUs may be a potential point of entry for attacks on the power system. To address this concern, we present Direct Time Estimation (DTE) for the robust GPS-based time transfer to PMUs. As a direct method, Direct Time Estimation (DTE) does not rely on intermediate measurements such as independent channel range, range rates and their residuals. Instead, it generates the time and time drift solutions by operating directly on the raw signal. In this manner, the entire received signal information is utilized, leading to increased robustness in tracking. We developed and implemented DTE on our research platform - PyGNSS. To evaluate the performance of DTE, we conducted realistic simulations, such as jamming and meaconing, based on data collected from field experiments. Through the simulated attacks, we demonstrate the enhanced robustness of DTE with respect to conventional algorithms, such as scalar tracking.