March 1, 2013. Difficulty rose by +19.63% to 4.37M from 3.65M.
Change
+19.63%
New difficulty
4.37M
Period length
11.7 days
Network hashrate then (7-day)
—
Bitcoin price then
$33
Hashprice then
—
The 2,016 blocks before it took 11.7 days instead of 14, so the network had more hashrate than the difficulty assumed, and difficulty rose by 19.63%: 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.