I am guessing that they are somewhere in Germany right now and its evening there. My speculation is that they landed in Frankfurt and took a train to another part of Germany like the Hamburg leg in Season 16 where it was done at night. Cities for my speculation: Mannheim, Dusseldorf, Worms, Cologne, Bonn, Nuremburg, Stuttgart, Dresden, Bremen, or Hanover. But the other option to my speculation is that Frankfurt could also just be an connection point to another part of Europe and with possible chances of visiting Finland or Latvia. If Finland is visited it would be the second time since Season 10 but this is only my speculation and nothing more.