What Was The Purpose Of Including A Timestamp In Older Postmarks?

speaking of conventional thinking, let's bear the reminder that the 1990s "sprays" were NOT postmarks in the conventional sense, but what postal workers call "stale meter daters," applied by sorting machines by the way.
They were supposed to be turned on when processing a tray of metered mail (as much was coming in from businesses that way, or from PO "metered' slotted collection mail) so that any "stale" (aged [wrong] date applied by mailer's meter!) would be corrected by the barcode sorter inkjet spray. Occasionally the switch was left on when regular trays were processed after metered tray (or I suppose some metered trays had mixed envelopes, anyone can put something in the "metered" slot at PO, right?)

I have a postmark in my collection that said 12:38 PM and was just wondering about this. Nice timing that it showed up in latest active topics!

I was just showing one of my old postcards to some friends when I went to their house for Thanksgiving. The overlapping Tokyo ("TOKIO") postmarks don't appear to include the time of day, but there are three New York receiving postmarks (or transit marks), which show the card's progress through the city on January 18, 1895: Station C 12–1 pm, Station D 1–1 pm, Station O 4 pm.