dmesg -T Has been available for years to print out human-readable timestamps. Check to see if dmesg is an alias to that on your system. Also, -IIRC- dmesg has

dmesg -T Has been available for years to print out human-readable timestamps. Check to see if dmesg is an alias to that on your system. Also, -IIRC- dmesg has printed system-uptime timestamps with every line since at least the early 2000's. One caveat: the times printed by dmesg -T will be incorrect if the system has suspended to RAM or disk. Check dmesg(1) for more info! :D