Dealing with part-time project members

Hi,
In our company we have quite a few people who work only part-time, e.g. some don't work on Wednesdays, some on Tuesdays etc. In addition, some work on specific days only part of the day. Is it possible to add an option to deal with such working times / days per "Contact"?
For example, I would like to be able to define that Joe is not available on Wednesday and then it would not be possible to schedule activities for Joe on Wednesdays. On the other hand it should be possible to manually "overrule" the availability of the employee on certain days when he / she is normally off.

Hello
I have the same issue, except that Joe is off every Wednesday afternoon.
-> I tried with FTE = 0.9 (like recommended in manual), but it generates an availability of 0.9 every day and that is not what is expected
-> Calendar (like recommended in this thread) allows to define only full days off
-> I tried with periodic meetings, it generates a lot of meetings and it requires lot of cpu if we want to edit the periodic meetings for a long period (like 1 year). And I could not set the meeting's project to "Administrative" type because in that case it does not appear in the planning. Then it works, but in "real work" interface, the resource can see all planned meetings (instead of only the meeting of the week) (existing ticket #1362 ). So that it not really satisfying.

What is the best solution to handle this ?

OK, I will experiment this
It is less work than defining periodic meetings anyway
Thanks !