Currently the next halving date is May 2020 (provisional) according to enter link description here.
I understand that every 210k blocks, the block reward is halved and this works out, roughly, to once every 4 years.
I guess I have two questions: 1) The 2012 halving took place approx. 3.8 years after genesis, and the 2016 halving took place a further 3.6 years after that. During this period hash rate increased almost continuously and at exaggerated rates due to continuous developments in mining technology from general to specific solutions (CPU -> GPU / FPGA -> ASIC). So were these 'premature' halvings due to the positive rate of change of hash rate?
2) A halving on 23 May 2020 is roughly 3.9 years from the last halving. It seems this is linked to 2018's drop in hash rate, could a hash rate collapse lead to a delayed halving event (i.e. adding the current 210,000 blocks takes longer than 4 years)?