September 4, 2015. Difficulty rose by +4.98% to 56.96B from 54.26B.
Change
+4.98%
New difficulty
56.96B
Period length
13.3 days
Network hashrate then (7-day)
0.4 EH/s
Bitcoin price then
$227
Hashprice then
$1,997/PH/day
The 2,016 blocks before it took 13.3 days instead of 14, so the network had more hashrate than the difficulty assumed, and difficulty rose by 4.98%: an ordinary adjustment. For every machine on the network that is a pay cut of the same size until the next retarget.