Health insurance premiums are normally due on the 1st of the month, but can sometimes be paid as late as the 30th of that month without the policy being canceled. That 30 day span is the grace period.
Some policyholders start to think of the end of the grace period as their due date, which causes problems if they’re a day late, for any reason. Big problems. “I’ve lost my insurance and can’t buy a new policy” problems.
Please remember that once you reach the grace period, payment is already overdue. Leniency is rarely granted if the grace period is exhausted, and someone may find themselves without coverage when they need it the most.