One of the things we need to do here is to be able to
declare things like:
"on this specific day, I spent 2.5 hours on this project
doing this..."
That means no predefined task, that means also no
specific hours, just time spent, and also simple interface
to enter/copy the time spent written on a piece of paper
(calendar, diary, whatever).
That means a use case of the type:
a user logs in, selects a client, and begins entering rows
after rows of time spent. The rows can be assigned to
some projects afterwards by his manager...
The way we work here, is we have an appointment with
a client, once in a while, we go there, do what we must,
note this on a piece of paper, then report it, then the
manager decides how much each action will be billed,
the client is shown the figures, agrees (or doesn't) and
then we bill him formally.