The subject matter is insured for a stated period of time, covering all risks from perils of the sea, pursuing any course. The policy is effective on the date of departure and terminates upon arrival at the port of destination, typically for a period not to exceed one year.
This allows for possible late departures due to weather, personnel or arrival of cargo. Should there be any likelihood that the delivery may be delayed beyond the policy period, policy holders should include a "continuation clause", such that the risk shall be covered until the voyage is completed at the port of call. (see "Voyage Policy" and "Mixed Policy")
Insurance ... simple and done!