Gust node log has a member field named 'timestamp', which is a uint64_t that records the time when the log packet is created inside node.
Note although in log the timestamp is represented as a 64bit unsigned integer, the node hardware only gives a resolution of 32bit scope, i.e., from 0 ~ 4,294,967,295.
The unit of the raw timestamp in log is in 'ticks', which is the count from timer of node hardware since powered on. To get the value represented in mili-seconds, divide the ticks by 32.768:
timestamp_ms = ticks / 32.768
Thus you can get the mili-seconds since the node is powered on.