The dollar soared against the yen Friday after the Bank of Japan shocked investors by cutting its deposit rate into negative territory—posting its largest daily gain against the Japanese currency since Oct. 31, 2014.

That date is significant for the BOJ; it was the day the central bank announced an unexpected expansion of its massive program of asset purchases as the Japanese economy struggled with the added pressure from recent tax hikes.

The yen USDJPY, -0.15% dropped to ¥121.34 to the dollar after the announcement—its weakest level in more than five weeks. Though it trimmed its decline to ¥121.06 to the buck late Friday in New York. The Japanese currency traded at ¥118.84 late Thursday in New York.

Market strategists were optimistic that the decision would result in further upside for the dollar in the near future.

“Currency markets will like this because now we’re seeing divergence again in monetary policy,” said Doug Borthwick, head of currency trading at Chapdelaine & Co.

The dollar also strengthened against the euro EURUSD, -0.06% and pound GBPUSD, -0.42% . The euro fell to $1.0832 late Friday, compared with $1.0932 Thursday. The pound fell to $1.4243, compared with $1.4359 Thursday.

Friday’s gains helped boost the dollar to slight monthly gains against the euro and the yen, while the rout in oil prices over the past month helped the buck book strong gains against resource-linked currencies like the Russian ruble USDRUB, +0.86% and Canadian dollar USDCAD, +0.29% .

Market strategists had largely ruled out the possibility of further easing at Friday’s meeting after the BOJ adjusted its massive program of asset purchases at its December meeting. Though many expected the central bank to convey a dovish tone and leave the door open for more stimulus in the future.

The dollar also benefited from a reading on economic growth in the fourth quarter that was roughly in line with the consensus forecast from a survey of economists polled by MarketWatch. The data, while unspectacular, helped dispel fears that the U.S. economy might have actually shrunk during that period.

“Traders are a little bit relieved that the pressure on price levels wasn’t worse,” said Matt Weller, a senior technical analyst at Forex.com. “It’s not a great report, but it’s not as bad as some expected.”