And pursuant to page 35 of United's contract of carriage

"Change in Schedule - When a Passenger’s Ticketed flight is affected because of a Change in Schedule, UA will, at its election, arrange one of the following:
1) Transport the Passenger on its own flights, subject to availability, to the Destination, next Stopover point, or transfer point shown on its portion of the Ticket, without Stopover in the same class of service, at no additional cost to the Passenger;
2) At UA’s discretion, reroute Passengers over the lines of one or more carriers in an equivalent class of service when a Change in Schedule results in the cancellation of all UA service between two cities;
3) Advise the Passenger that the value of his or her Ticket may be applied toward future travel on United within one year from the date of issue without a change or reissue fee; or
4) If the Passenger is not transported as provided in C) 1) or 2) above and does not choose to apply the value of his or her Ticket toward future travel as provided in C) 3) above, the Passenger will be eligible for a refund upon request."

https://www.united.com/web/format/pdf/Contract_of_Carriage.pdf