In Denmark, when the sovereign is abroad, a member of the RF must stay "at home" and act as regent.
I know that Pr.Frederik and Pss Benedikte acted as regents for brief periods 2-3 days while Q.Margreth was abroad in official or private visits.

Is it necessary to appoint a Regent in Copenhague if the sovereign visits Greenland or the Faroyar Islands, or, in such cases, it is considered the sovereign is "at home" and there is no need of a Regent ?