December 18, 2015. Difficulty rose by +18.14% to 93.45B from 79.10B.
Change
+18.14%
New difficulty
93.45B
Period length
11.9 days
Network hashrate then (7-day)
0.7 EH/s
Bitcoin price then
$457
Hashprice then
$2,523/PH/day
The 2,016 blocks before it took 11.9 days instead of 14, so the network had more hashrate than the difficulty assumed, and difficulty rose by 18.14%: one of the largest adjustments on record. For every machine on the network that is a pay cut of the same size until the next retarget.