5 The health insurance has a retroactive effect, if necessary in deviation from Article 925, first paragraph, of Book 7 of the Dutch Civil Code:
a. if it commences within four months after the insurance obligation arose, up to and including the day on which that obligation arose;
b. if it commences within one month after a previous health insurance has been terminated by cancellation with effect from 1 January of a calendar year or due to a change in the conditions pursuant to Article 940, fourth paragraph, of Book 7 of the Dutch Civil Code, up to and including the day after the day on which the previous health insurance ended.