Time Message Fields
A Time message is immediately generated and sent when there is a TOP event for a given clock second. If there is no new sequenced TOP event for a given clock second, then no Time message is sent for that second. All subsequent Time Offset fields for the same unit will use the new Time value as the base until another Time message is received for the same unit. The Time field is the number of seconds relative to midnight Central Time, which is provided in the Time Reference message. The Time message also includes the Epoch Time field, which is the current time represented as the number of whole seconds since the Epoch (Midnight January 1, 1970).
| Field Name | Offset | Length | Type/(Value) | Description |
|---|---|---|---|---|
| Length | 0 | 1 | Binary | Length of this message including this field. |
| Message Type | 1 | 1 | 0x20 | Time message |
| Time | 2 | 4 | Binary | Number of whole seconds elapsed since the start of the current Central Time calendar day, derived by converting the current Central wall clock time (HH:MM:SS) to seconds. On Daylight Saving Time transition days, Time reflects wall clock seconds and does not adjust for the UTC offset change. On a DST spring-forward day, the maximum value will be 82,799 (23 hours). On a DST fall-back day, values between 3,600 and 7,199 will appear twice. Recipients requiring unambiguous absolute timestamps should use Epoch Time (where available) or Midnight Reference in the Time Reference message. |
| Epoch Time | 6 | 4 | Binary | Number of whole seconds since the Epoch (Midnight January 1, 1970 UTC). |
| Total Length = 10 bytes | ||||