FlyerTalk Forums - Check Your UA Itineraries for Schedule Changes and what to do after one

UA typically updates schedules on late Wednesday & Friday evenings into the next day morning (USA Central Time).

United's FAQ on Schedule Changes webpage is no more vague but the follow seems to be the present policy

-- reschedule flexibility for 30 minutes or more changes

Your origin and destination will have to be the same as on your original itinerary.
If you have a connection, you may be able to choose a different connecting city or airport.
Alternative flights must be operated by United or our United Express® partners.

-- refunds for 2 hours or more changes
--- we may be able to offer you a refund:

The scheduled departure or arrival time changes by two hours or more.
The change causes issues with the overall length of the trip, such as making the connection time too short or significantly longer than it was originally.
If we are unable to accommodate you in the same cabin as purchased – refunded either the full price or the difference in fare.

If you're not satisfied with your new itinerary and one of the above scenarios applies, please don't accept the itinerary in Manage Reservations. Instead, you can request a refund online.

Generally, UA is pretty good about being flexible if you are adversely affected by a schedule change. Most reasonable requests will likely be honored. Best to do some self-research prior to calling. Including opening up award space on UA operated flights. If you had a cleared upgrade on UA operated flight, UA will generally honor that in the rescheduling if space is available (but not requiring upgrade inventory space on the new flights)

During this weekend change period and sometimes for a day later, there can be weirdness in displayed aircraft or seating maps, such as Strange/Impossible Aircraft Assignments After UA's Weekend Schedule Update

Early in the COVID pandemic, UA initially change the policy for refund to require 24 hour change, but quickly walked that back to 6 hours. Under DOT and public pressure, UA returned to a 2 hour policy on 6 June 2020. 30 minute change is still the threshold for flexible rebooking

More specific information is found in UA's guidance to TA's (on Jetstream) on re-scheduling

Quote:

Any segment goes from a non-stop to a connection
Misconnecting itinerary
Change to originally scheduled arrival or departure time of at least + / - 30 minutes

Change to alternate flight (original operating carrier or carrier permitted as noted in fare rule) or UA operated flight. If itinerary includes UA operated segment, UA schedule change rules apply to that segment {meaning changing only to UA operated flight}.
Same booking class. If original booking class unavailable, book lowest available (higher than original booking class, same cabin) up to and including M class. Contact UA if required class of service is unavailable.**
Change fee and add/collect waived - see "Additional parameters for flights impacted by schedule changes" below the chart.

For 2 hours or more, refunds are an option unless you can be rescheduled to be under the 2 hours

Quote:

Change to original arrival or departure time of 2 hours or more or cancelled flight with no protection

Quote:

or
Additional parameters for flights impacted by schedule changes

Non-stops may go to connecting flights, and connecting flights may go to non-stops
Connecting hub may be changed
If original day of departure is unavailable, may depart 7 days prior to or after original departure date. If outbound flight is impacted, subsequent flights on same itinerary may be changed to maintain original length of trip.***
Alternate airports within a 250 mile radius of the original origin or departure airport***
- Change may apply to origin and destination, but must be changed at the original time of ticket reissue
- Customer is responsible for any additional expenses incurred

Please see footnote below regarding the handling of United Basic Economy fares booked in "N" class.

***Continuing or return travel dates may be voluntarily changed on UA segments only in the original inventory class to maintain the original length of stay prior to the re-accommodation. Changes to the return flight must be in the same PNR and be made in the same transaction as the re-accommodation of the outbound flight. The change fee and add/collect will be waived for changes made to the return (original class of service only).

**United Basic Economy fares booked in "N" class must remain in "N" class when eligible for self-service rebooking due to unacceptable schedule changes or irregular operations. If "N" class is unavailable, please contact United’s Customer Contact Centers for assistance. Rebooking into an ineligible booking class may result in the issuance of a debit memo. For non-Basic Economy fares, do not rebook into "N" class.

================= older information =======================
The peak-time for changes is roughly 3-4 months prior to departure but changes occur anytime -- especially aircraft changes within an aircraft family (such as 777-200s or 737-800 vs 737-900).

Schedule changes

Quote:

Rebooking options if a schedule change has affected your itinerary

If your scheduled departure or arrival time changes by 30 minutes or more, we're happy to try to find other available flight options that meet your needs. Please keep the following in mind when you call:

Your origin and destination will have to be the same as on your original itinerary.
If you have a connection, you may be able to choose a different connecting city or airport.
Alternative flights must be operated by United or our United Express® partners.

If we aren't able to find any other flights that meet your needs, requesting a refund may be an option. See the section below for more information.

Ticket refunds

When a schedule change happens, we try our best to provide you with options that minimize the disruption to your travel plans. In cases where the new flight options don't work for you and one of the following scenarios applies, we may be able to offer you a refund:

The scheduled departure or arrival time significantly changes.
The change causes issues with the overall length of the trip, such as making the connection time too short or significantly longer than it was originally.
If we are unable to accommodate you in the same cabin as purchased – refunded either the full price or the difference in fare.

If you're not satisfied with your new itinerary and one of the above scenarios applies, please don't accept the itinerary in Manage Reservations. Instead, you can request a refund online.

It is reported that agents will now (12 March 2020) process refunds for 6-hour changes (down from the original new 25+ hours that replaced the previous long practice of 2-hours)
JetStream - Agency Rebooking Parameters