https://support.communitybrands.com/hc/en-us/community/posts/30757472013581--1-888-829-1467-How-many-days-before-a-United-flight-can-you-change-the-date


Well, United Airlines allows passengers to change flights up to 24 hours before their scheduled departure time, for free and with no penalties. After the 24-hour period, United Airlines Change Fees will be $200 to change the date and time of their flights.A simple way to change or cancel a flight without paying a fee is to do so within 24 hours of booking.