On major holidays, DCL tries to book an appropriate clergy person to perform services for guests. This will be noted in the Navigator. They do this for most Jewish and Christian holidays.
If an appropriate religious official (of any religion) is on board and OFFERS to perform services, space will be provided and a notice placed in the Navigator. Whether these services are daily, once during the cruise, or whatever is up to the volunteer.
On cruises with no clergy, DCL makes space available on Friday evenings for Jewish services and Sunday mornings for Christian services. These are a situation where all interested individuals may have a "do it yourself" service.
There are no services or space available on cruises beginning or ending on a Sunday. There is a list of churches available at Guest Services for individuals who may wish to attend at a church near the terminal.