On 6/21/19 07:57, Quan Zhou wrote: > Yep, went through the same route until I figured out that GPS time is a > bit ahead of UTC. The data from GPS includes the offset value from UTC for leap-second correction. This should be easily included in your time calculation. It's presently 18 seconds. -- Jay Hennigan - jay at west.net Network Engineering - CCIE #7880 503 897-8550 - WB6RDV