You first must answer the question, are you fully vaccinated as per the EHAS travel requirements. If you are fully vaccinated than you have 3 calendar days, prior to the date of departure on your final leg, in order to submit your EHAS application. For example, If the final leg of your flight to St Maarten departs on Saturday then you can submit your EHAS application starting anytime on Wednesday or later. 72 hours no longer has anything to do with submitting your EHAS application. If you require a test It is either 48 hours(PCR) or 24 hours(Antigen) depending on the type of test submitted.