A message timestamps communication
The time shown beside a message usually tells you when that message was recorded in the presented thread. It does not automatically timestamp every event mentioned in its text. Someone can write at 19:00 about a visit at noon, repeat yesterday's news or describe a plan that never happens. Read the verb tense and any explicit time reference before putting the described action on your timeline.
Worked example: already home
A message at 18:40 says I was already home when she called. The message time alone does not establish when the person arrived, or when the call happened. You need the call's timing and an account of arrival to narrow the sequence. Writing home at 18:40 may be a reasonable limited observation about the claim, but it should not become arrived at 18:40.
Use two linked entries
When the distinction matters, make one entry for the message and another for the event it describes. Connect them as source and claim rather than merging them into a single timestamp. This keeps later discoveries easy to incorporate. In Somatry, a thread can be valuable evidence while still containing recollection, inference or plans; its neat sequence on the screen does not make every described event happen in that same sequence.