The Confirmation Date will automatically be set to either 365 days after the last confirmation date or 365 days after incorporation if no confirmation statement has yet been filed. It is possible to change this.
Once a Confirmation Statement is submitted, the Confirmation Date for the following year is the same date on which it has just been submitted.
I.E. You file a Confirmation Statement on 18/05/2022. The next confirmation date is then 18/05/2023.
So whenever you successfully submit a Confirmation Statement you reset the clock and have another 365 days until you must file the next one. This date becomes the next Confirmation Date.
In the above example, you could change the confirmation date for 2023 to 01/08 by filing a Confirmation Statement on 01/08/2022.
You cannot change the Confirmation Date in any other way.
For more information:
What Fees Do I Pay to File a Confirmation Statement?
Can I File More Than One Confirmation Statement Per Year?
Why Might I File a Confirmation Statement Early?