Yes! You have the ability to book a shoot without a date specified at the time of booking. On the Shoot screen for the job for which you are creating a proposal, simply click "Book" and you'll be prompted to create your proposal.
Keep in mind that when there is no date selected, you'll be prompted to choose a payment schedule that is not related to the Shoot Date.
In addition, if you have the variable for "Event Date" or "Event Coverage Date/Time" in the contract you're using for this Shoot, this variable space for the date will show up as blank since no date was chosen.
You will not be prompted on the proposal screen to select a workflow if there is no date specified for the shoot. A workflow can be added to the shoot later, after a date is selected.