A travel day is valid from 0:00 until 23:59. Only if you enter a train before midnight and do not change to another train, you don't need a new travel day. And of course you can use two (or more) travel days in a row.

Be warned though that there are currently no international trains from/to Greece and nobody knows when there will be again. Maybe in summer from Sofia…

The most comfortable way to get to Greece is currently to use a ferry from Italy.

Ahh okay thanks! I was wondering why I couldn't get a route with the interrail planner haha! I want to go by land, but I might look at the ferry, thanks for the tip! I am planning to do the trip this summer, or maybe next year, depends on the state of everything

a travelday is from 00.00 till 23.59 :)

The Nighttrain rule (most important for Flexipass users) means that if you board a train before 23.59 you can even write on this train in to the next day Crazy example is to catch the Euronight from Vienna 19.42 to Bucharest arrival at 16.00 the next day :)

There are two major kind of passes :)

Continouspasses means everyday within the validity time is a travelday (you can ride on any day) From just 7days up to 3 months

Flexipasses you have a specific amount of travelday´s within the validity period From 4days within a month up to 15days in 2 Months :)

Amsterdam Athens is pretty long and currently just possible by Rail & Ferry from Italy as currently no International train reach Greece (There used to be before 2020 direct connections from Bucharest - Sofia or Belgrad - Skopje to Thessaloniki )

You will need atleast 2 Traveldays
3 traveldays are better