Hover over the date or time on the Conversation Timeline to see an event’s exact date and time. For example, the image below shows Mar 17. Hovering over the date shows that Adam replied to the email on Mar 17, 2022, at 6:32 pm. The date/time appears for incoming and outgoing Contacts. Additionally, this works for Tasks and Notes as well.
The timestamp is based on the first message for a block of consecutive messages.