Your commands did not work on both Cloudshell and EC2 Linux. Here are outputs

#Cloudshell

[cloudshell-user@ip-10-130-70-166 ~]$ aws rds describe-db-cluster-snapshots --query "DBClusterSnapshots[?SnapshotCreateTime<='$(date -v -30d '+%Y-%m-%d')'].[DBClusterSnapshotIdentifier, DBClusterIdentifier, SnapshotCreateTime, Status, Engine]"

date: invalid option -- 'v'

Try 'date --help' for more information.

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[cloudshell-user@ip-10-130-70-166 ~]$ aws rds describe-db-cluster-snapshots --query "DBClusterSnapshots[?SnapshotCreateTime<='$(date -30d '+%Y-%m-%d')'].[DBClusterSnapshotIdentifier, DBClusterIdentifier, SnapshotCreateTime, Status, Engine]"

date: invalid option -- '3'

Try 'date --help' for more information.

#EC2 Linux

[ec2-user@ip-172-31-26-154 ~]$ aws rds describe-db-cluster-snapshots --query "DBClusterSnapshots[?SnapshotCreateTime<='$(date -v -30d '+%Y-%m-%d')'].[DBClusterSnapshotIdentifier, DBClusterIdentifier, SnapshotCreateTime, Status, Engine]"

date: invalid option -- 'v'

Try 'date --help' for more information.

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[ec2-user@ip-172-31-26-154 ~]$ aws rds describe-db-cluster-snapshots --query "DBClusterSnapshots[?SnapshotCreateTime<='$(date -30d '+%Y-%m-%d')'].[DBClusterSnapshotIdentifier, DBClusterIdentifier, SnapshotCreateTime, Status, Engine]"

date: invalid option -- '3'

Try 'date --help' for more information.

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It does not like -v option. Is there any other option I should try?

Thanks much