how to implement holyday voicemail in amazon connect?

This is possible by setting the operation time.
However, this method can be used for simple holidays (e.g., only Saturdays and Sundays), but not for holidays that occur unexpectedly.
https://docs.aws.amazon.com/connect/latest/adminguide/set-hours-operation.html

In order to accommodate unexpected holidays, the calendar must be created using the Systems Manager Change Calendar.
From there, I think it would be possible to use Lambda or similar to determine whether the day on which the call is attached is a holiday or not.
https://docs.aws.amazon.com/systems-manager/latest/userguide/systems-manager-change-calendar.html