Gregory is going away for the holidays.

Phuc, 

there is a ‘ specific ‘ duration - the duration of ‘the holidays’, a period of time with a definite start and end.

Not all ‘ clear beginnings and ends ‘ have to be specified with days or weeks etc, dates or time. A clear beginning and end can be established by reference to something that in context would either be known, or could be established/confirmed. It could be explicit or implicit.