Embarkation x Boarding: What's the difference?

Como você pode verificar no dicionário, "Boarding' é o ato de liberar o acesso dos passageiros. Ex: Avião, ônibus, trem.

O "Embarkation" também é o ato de liberar passageiros para embarque em avião ou navio. Mais comumente usado em embarcação de navios.

Neste link: http://www.english-test.net/forum/ftopic66297.html
Há uma explicação sobre "Embarkation":

'Embarkation' is the act of getting passengers and crew on board a ship or plane. As this is specific to shipping.

Abraços,

I would say that "embarkation" is getting out of date, in our contemporary age. They may favor "boarding" over "embarkation". Perhaps use by navigation companies, though. Of course, I don´t mean other related words, like "embark" etc.

Ref. thefreedictionary

A. The act of embarking on an aircraft, train, ship, etc

Grammatically speaking, I think your sentence might be okay, but "when the embark is going to take place?/starts" would be a more natural version.

When the embarking is going to happen/to take place, etc.
Would be a more apt way to say that.

Let´s wait further comments on that one.