People travelling to Jersey from regions which are due to change from amber to green under the first changes to the island's latest travel restrictions will still be treated as amber arrivals until after 18 May.
More parts of the British Isles will be classed as green from Tuesday 4 May, but officials are reminding passengers that their travel history over the past 14 days will be taken into account.
The area must have been classified as green on the government website for the whole of those 14 days to qualify for the lower isolation period, until the passenger receives a negative result from their day zero test.
For example, passengers from Birmingham, who arrive on 7 May will have spent 10 of the previous 14 days in an amber area, so will have to isolate for as if they have been in an amber area for the whole period.
To qualify for green arrival status, a person travelling to the island must have only slept in areas that were classed as green when they spent the night there.
The government says travellers from newly 'green' regions will have to wait until Tuesday 18 May to be eligible to travel under the 'green' testing regime.
Passengers in regions which are moving from green into amber from Tuesday 4 May are advised they should leave those regions before 23:59pm on Monday (3 May) - either by returning to Jersey or moving to a green region - if they want to be treated as a 'green' arrival when coming into the island.