not sure if official waiver but:
Because of winter weather affecting areas of Colorado on March 31-April 1, we are offering additional flexibility that may allow you to change your travel plans. See united.com/importantnotices for details.
Your travel is important to us, and we'll make every effort to prevent unnecessary disruptions.
Please be sure to check flight status on the United app or at united.com/flightstatus before going to the airport, and sign up to receive flight status messages in the event of changes.
Thank you for choosing United.
I was able to change ewr-den-las to EWR-LAS