Template: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 7 May 2007 chart and 4 June 2007 chart demonstrate a change near June 2007.
 * According to this and the very bottom of this, from 17 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.