The Bulk Electric System (BES) is a key critical infrastructure element necessary for the operation of nearly every industry in the United States. Modern power system applications, such as phasor measurement units , require highly accurate time-of-day  synchronization, typically within ±1 µs. Some applications demand even greater precision, with time signals coordinated across multiple locations. Currently, coordinated universal time via Global Positioning System signals is the primary source of precise timing for control, protection, and disturbance analysis in the BES. However, reliance on GPS as a single source introduces risks. To address this, the Pacific Northwest National Laboratory (PNNL) is leading an effort for the U.S. Department of Energy to identify alternative and complementary timing sources for the electricity industry. The effort includes test and evaluation of non-GNSS solutions, industry outreach, and updates to the DOE PNT Profile for the energy sector. This presentation will: Describe the timing threat to the BES, how our project partner, the Bonneville Power Administration, a federal Power Marketing Administration operating much of the BES in the Pacific Northwest, identified the weakness of GPS as a single timing source several years ago, Detail BPA’s response, which included integrating an alternative timing source and distribution method (using IEEE 1588) to their protection roadmap. BPA has completed three phases of test and evaluation, with the latest phase involving at-scale testing on their transmission system. Additionally, the presentation will highlight a PNNL developed testbed designed to evaluate the performance and compatibility of various timing systems, both sources and distribution methods, against the specific needs of the electricity sector. The testbed uses a hybrid hardware-in-the-loop simulation environment to evaluate how various approaches work with real-world scenarios including: The effects of jamming and spoofing of PNT sources The impacts of timing disruptions on both local applications (transmission line protection), and wide-area applications (control center operations). The presentation will explain how additional users, technologies, and vendors can become involved in the testing. Lastly, this presentation will cover PNNL’s involvement in standards development, including contributions to: IEEE P1952, Standard for Resilient Positioning, Navigation and Timing (PNT) User Equipment IEEE P2030.101, Guide for Designing a Time Synchronization System for Power Substations. Following the presentation, attendees will have a better understanding of the timing needs of the electricity sector and the risks posed by inaccurate time, which can lead to unintended operations or inefficient use of resources.