If you need to change your flight date, you can do so up to 24 hours before the scheduled departure, as long as you keep the same route and cabin as in the original booking. Changes are subject to availability at the time you make the request.

The cost of the change depends on whether your booking includes a Flexible Ticket.
Booking with Flexible Ticket: The first date change has no change fee. You will only need to pay any fare difference. 
If your booking does not include Flexible Ticket: The change fee is €150 per flight, plus any fare difference. 
 

Conditions
Changes are allowed up to 24 hours before the departure of the original flight.
The change will apply to everyone in the booking, as it cannot be made for only one passenger.
You cannot change the origin, destination, or selected cabin.
If you had already purchased a seat, we will refund the full amount as a voucher so you can purchase a seat on the new flight or use it on a future trip. If seat selection is included in your fare, you will be able to select a new seat.
Date changes are not allowed on connecting flights. If you need to change your trip, you will need to make a new booking under the applicable conditions.
If you made a mistake when booking, you have 24 hours from the time of purchase to change the date without paying a change fee. You will only need to pay any fare difference. You can do this by contacting us through any of the channels available in our Help Center.
If you booked through Iberia.com, a travel agency, or another third party, you must request the change directly through that channel.
How do I change my flight date?You can change your flight date in the My booking section:

Access your booking using your booking code and email address or last name.
Select “Change your flight”.
Select the flight, choose the new date, and confirm.
Make the payment, if applicable.
You will receive an email with your new flight details at the email address provided in your booking.

In the following cases, you will need to contact us through one of the support channels available in the Help Center:

Connecting flights
Bookings with an infant
Bookings made with a promo code
Flights with a purchased seat