Just look at these examples:
Why can't they be consistent?
I don't really want to know the day of the week when something was posted, but I always want to know the date, and the time.
So why can't the software always display the date and time of the post?
Why display only the date when it was several days ago? And why not add the time?
Also, why display the date and time in a quoted post, but not in the original post?:
This inconsistency just doesn't make sense.
You can add the day of the week if you want, but I don't think it is a hard thing to do to always display the date and time of a post, as in the quoted post above.