I don't think you'd need to further complicate DNS, just have a service running that checks a calendar and syncs your DNS TTLs appropriately. eg. - Check if t

I don't think you'd need to further complicate DNS, just have a service running that checks a calendar and syncs your DNS TTLs appropriately. eg. - Check if there's a maintenance window in the next [max TTL] - If not, set TTL = [max TTL] - Otherwise, set TTL = [time until maintenance window] - Repeat