User:Muhandes/Certification Table Entry/Sales/NewZealandPeriod/doc

This helper template calculates periods for New Zealand single certifications, as stated in the following sources:
 * According to the levels changed in 1989.
 * The [//web.archive.org/web/20130613001808/http://www.rianz.org.nz/attachments/rianz/chart-1563-07-may-07.pdf 7 May 2007 chart] and [//web.archive.org/web/20140119193025/http://www.rianz.org.nz/attachments/rianz/chart-1567-04-jun-07.pdf 4 June 2007 chart] demonstrate a change near June 2007.
 * According to this and the very bottom of this, from June 2016, the NZ singles have 15,000 for Gold and 30,000 for Platinum now.

It returns:

Returns 0 if the data provided is not sufficient.