Diagnosing time differences between devices

Define the difference before changing settings

Record the two devices or timestamps being compared, the size and direction of the difference, and whether it is fixed, increasing, intermittent or present only after a restart. Compare the same UTC/local basis and date. Screens refreshed at different moments are not a precise clock-offset measurement.

For an NTP/PTP client, use the timing measurements reported by that client where available. For physical timing outputs, compare the signals using measurement equipment suitable for the required accuracy. Record the method so a displayed refresh delay is not mistaken for clock drift.

Trace the reference to the affected destination

1. Reference: record the source selected by the master clock and whether it reports lock, holdover or an unavailable reference when the error occurs.
2. Distribution path: record the NTP server address, PTP source/domain or time-code output feeding the receiver. If a DA12 is present, identify its input, output bank and affected destination. Compare another destination on the same source to determine whether the problem is shared or isolated.
3. Receiver: distinguish “receiving packets/signal” from “synchronized and using this reference.” Record the selected input and synchronization status.
4. Displayed result: compare the receiver’s own time with the application or display being reported. Check whether that application uses system time, an independent clock or cached status.

Use the error pattern to choose the next check

• A stable whole-hour difference: Displayed time is off by whole hours.
• Time code decodes but the date or UTC value is wrong: Wrong UTC time or date when using time code input.
• The difference grows after reference loss: Time Dissemination During Reference Outages.
• The client is not receiving NTP updates: NTP clients not receiving updates.
• PTP shows a consistent timescale offset: PTP time appears 37 seconds offset from UTC.
• Only one DA12 destination loses its signal: DA12 has power, but is not outputting time code.

Evidence to provide to Support

Include model and firmware, the reference/distribution path, source and receiver status captured at the same time, the actual offset and comparison method, and a short record showing how the error changes. Include any network, cable, input-selection or time-zone changes that preceded the issue. This identifies which stage needs investigation without changing unrelated settings.