https://support.communitybrands.com/hc/en-us/community/posts/30758231540109-1-888-829-1467-Can-I-UpDate-Date-On-United-Ticket-Online

Keep in mind that certain fares may have restrictions, and you might incur additional fees or fare differences when changing your flight.Keep in mind that certain fares may have restrictions, and you might incur additional fees or fare differences when changing your flight.