Check In/Check Out Widget: How to allow past dates on the widget?

Is there a way to allow the Check In/Check Out widget to select past dates?

I do not think that this is possible, the widget will allow you to set the current date and future dates, it was designed to do that and this is its functionality. 

If you want to allow past dates you will need to use either the Date Time field in the Form Builder  or another widget. 

You will find the date time field under the Quick Fields in the Form Builder: 

These widgets will help you to get dates as well. 

Date Picker. 

Date Reservation. 

Large Date  Picker. 

Hope this helps. 

So there's not any CSS you can use to allow this? I just want to be sure before I switch to the DateTime field. I'm trying to stay consistent on my forms and the other widgets have already been eliminated as possibilities. 

No, this does not work with CSS codes to allow or not the selection of a date, it is required to use Javascript codes to do that, something that is not possible to do, you can not add Javascript code in the widget nor the form. 

The only way here would be using some of the widgets provided above or as you decided the Date Time field that will allow you to do what you need.