Well, it won’t be needed after all. I just got an email from United stating that the test window is 120 hours.


Destination: St. Maarten
Test type: Molecular: PCR or Antigen/AG
Timing: Test results must be dated no earlier than 120 hours before your departure from Washington (IAD) to St. Maarten (SXM)

Based on your itinerary, your test results must be dated no earlier than February 08, 2021.

Other information that may be required before boarding or entry:

Complete Sint Maarten's Electronic Health Authorization at least 12 hours before departure at https://stmaartenehas.com/.

This continues with more detail, shortened for brevity’s sake.