PTP time appears 37 seconds offset from UTC

• PTP client devices display time approximately 37 seconds different from UTC, NTP, GPS/GNSS, or other time displays.
• The GMR appears synchronized, but one or more PTP clients show a consistent offset.
• The offset remains close to 37 seconds instead of drifting gradually over time.

• PTP can use a TAI-based timescale instead of UTC. TAI does not apply leap seconds the same way UTC does.
• Some downstream devices expect UTC-based time and may display a 37 second offset when receiving PTP time using the PTP (TAI) timescale.
• The PTP timescale setting on the GMR does not match the timescale expected by the downstream PTP client.

1. Confirm the offset is approximately 37 seconds.
   A consistent 37 second difference usually points to a PTP timescale interpretation issue, not clock drift.
2. Open the PTP Time Properties settings in WinDiscovery.
   Open Device Settings, select Precision Time Protocol, then select Advanced and open the Time Properties tab.
3. Review the PTP Timescale setting.
   The GMR can be configured for PTP (TAI) or UTC (ARB), depending on what downstream devices expect.
4. Select the timescale required by the downstream devices.
   Use PTP (TAI) for devices that expect PTP time based on TAI. Use UTC (ARB) for devices that require UTC-based PTP time.
5. Verify the client display after the setting is applied.
   Confirm that the PTP client reports the expected time after the GMR resumes PTP grandmaster operation.

• PTP clients show the expected time after the timescale setting is applied.
• The 37 second offset is no longer present on devices that require UTC-based time.
• The GMR remains synchronized and continues operating as the PTP grandmaster.

Time Dissemination During Reference Outages