Let user specify a time

I'd like a summary that shows all the "picked" dates but ordered by most picks.

The ability to choose multiple non-consecutive days. So when planning a reoccuring meeting that is spread over months (IE a day in Sept + a day in Oct) you can easy do this in one calendar instead of multiple calendars.

Let users leave comments

I want to arrange an event on a weekend so want to make only Saturdays and Sundays available for selection without having to go decline every weekday.

Sometimes people need reminders to respond to the initial request.

Create a facebook app that provides the functionality of facebook useful for planning events for a group.

The planning process often requires multiple emails to the greater group and doing this via whichdateworks eliminates the need for multiple email chains.

In the case where I've invited someone who doesn't have access to the site to select their own dates (like my old Aunt who doesn't have a computer, someone on vacation without the internet or The Queen) it would be nice if as the meeting organizer I could select dates for them so they can be counted in the whole group.

Awesome so far, thanks!

Add an option to change how the calendar looks, so that in countries where the work week is different from the American standard, you can just choose a different day in which the week starts.

this would be great as an iPhone app.

This is so close to being incredibly easy to use but it is missing one thing... As an invitee, I cannot see the dates that the organizer (first person) picked. They could be this week, next week, next month -- I don't know until I click on that person.
I want to view the dates selected by others WHILE selecting my dates. That would make this the best tool out there.
Plus the time of day feature mentioned by another already. Gotta have that to schedule business meetings.

I can't figure out how to add people to the distribution list without sending a new email to everyone on the list

Mouse-over a name to show only their availability. Select a list a name, to add or remove them from a filtered calendar. Executives come first, so I want 1 view of everyone, 1 view of availability of the most important people, and then to see only the CEO's availability to make sure the meeting works for him.

PS: otherwise the site is awesome.

The plaxo.com plug-in sometimes hangs or doesn't work. Users have asked for a better solution, vote here if you agree.

Make it easier to arrange:
- holidays lasting 1 or 2 weeks
- trips at weekends
- meetings lasting several days

Users can select which time works best within an individual date