To remove records older than a week (7 days) from the journalctl log records:
journalctl --vacuum-time=7d
Tag: journalctl
Very specific time from journalctl log
Run:
journalctl -o short-iso-precise
Results:
2018-09-19T23:30:11.651010-0400 linux05.domain.ccTLD process[PID]: Log message here.