Hi,
from the day you change your status to graduate, you have the right to start receiving dagpenge within 2 years (without further requirements).
You only need to inform the A-kasse, if you receive dagpenge at the time you go on holiday.
When you come back to Denmark, you only need to register as unemployed at Jobnet.dk, and tell your A-kasse that you now want to receive dagpenge.
If you have not used any of your dagpenge, before going on holiday, then you will have the right to receive dagpenge for a 2 year period.
Best regards,
Anders Weber, www.a-kasser.dk