How to change the backup window time for Amazon RDS with continuous backup enabled in AWS Backup

Issue

When I created a backup plan with continuous backup enabled in AWS Backup and assigned it to an Amazon RDS DB instance, the backup window time was changed.
Is it possible to change the backup window time?

How should I handle this?

When continuous backup is enabled in AWS Backup, the automatic backup settings for Amazon RDS are managed by AWS Backup, and the backup window is automatically adjusted to avoid conflicts with the maintenance window.

Therefore, if you want to explicitly specify the backup window, do not use AWS Backup and instead manage automatic backups from the Amazon RDS side.

https://docs.aws.amazon.com/ja_jp/aws-backup/latest/devguide/point-in-time-recovery.html#point-in-time-recovery-supported-services

RDS
Backup schedule: When an AWS Backup plan creates both Amazon RDS snapshots and continuous backups, AWS Backup intelligently schedules the backup window to coordinate with the Amazon RDS maintenance window to prevent conflicts. To further prevent conflicts, manual configuration of the Amazon RDS automatic backup window is not available. RDS creates a snapshot once a day even if your backup plan has a snapshot backup frequency other than once a day.

Reference Information

• Continuous backups and point-in-time recovery (PITR) - AWS Backup