With entry into force of "International Convention for the Control and Management of Ships' Ballast Water and Sediments, 2004", IOPP and/or BWM Certificate (issued by some flag states) may be de-harmonized from Harmonized System of Survey and Certification (HSSC).

In this case, the ship owners may be required to arrange periodical surveys twice a year, if the survey window of the de-harmonized IOPP and/or BWM Certificate does not overlap enough with the one of other statutory certificates including SC Certificate.

As a way to reduce such burden to arrange periodical surveys twice a year, the owners can carry out periodical surveys in advance of the survey window and amend the anniversary date. By amending Anniversary Date, it would become easier to arrange periodical surveys once a year, because the de-harmonized survey windows are overlapped with others in longer period.

Figure below shows a case study that, in case where the survey window of de-harmonized IOPP/BWM Cert. is little overlapped with the survey window of other statutory certificates including SC Certificate, periodical survey (Annual Survey) of de-harmonized IOPP/BWM Certificate is carried out in advance and the anniversary date is amended.