Hello jiantongglobal-t-bird-edu,
First of all thank you very much for using the plugin.
Currently, the plugin has the feature where you will be able to add the multiple pricing according to your preferred dates. If the dates for that particular pricing is not available then you need to update the pricing manually.
But if you want the automatic updates of the days then you need to hire a customizer.
To hire a customizer please refer to below given link:
http://wptravel.io/hire-wordpress-customizer/
Additionally, we do have addon WP Travel Utilities using which you can provide the piece of information whether the trips is sold out / out of date. Not only this with this addon you can enjoy multiple features and to know about it please refer to below given link:
http://wptravel.io/documentations/wp-travel-utilities/
Thank you.
Best Regards!!