Way Day, Wayfair Inc.’s inaugural one-day sales holiday, last Wednesday generated the retailer’s biggest-ever day in terms of revenue, CEO Niraj Shah told investors on Wednesday during a conference call with analysts.

Wayfair’s e-commerce sales reached $1.39 billion in the first quarter ended March 31, up from $940.4 million in the year-ago time period. In the U.S., e-commerce sales increased 42.1% to $1.19 billion in the quarter up from $837.6 million a year earlier. Wayfair is No. 13 in the Internet Retailer 2018 Top 500.

Wayfair promoted Way Day on TV, in direct mail, email, social media and other channels and Shah hinted the one-day sales event will be an annual event. “We expect that the event will grow further for us in future years.”

There’s good reason for that bullishness. Wayfair drove a roughly 400% jump in sales compared to the average daily sales orders from the previous month, according to new data released by Edison Trends. The retailer also boosted the number of unique visitors on its sites and apps nearly 400% compared to the average from the previous month.

Wayfair had 2.5 million U.S. site website visits on Way Day, which was April 25, a 92.3% jump from the 1.3 million visits it had on the same day a year earlier, and a 66.7% increase compared to the average daily visits from April 3-30 (excluding April 25), according to digital measurement firm SimilarWeb Ltd.

Moreover, the shopping event drove consumers to dig deeper into the retailer’s website. Consumers looked at 11.4 pages per visit, a 67.6% increase from 6.8 pages over the April 3-30 period. And they spent more than 10 minutes on the site compared to less than 7 minutes.

While Wayfair invested heavily in advertising Way Day, direct traffic was its biggest source of traffic. Its more than 570,000 visitors who typed in Wayfair.com accounted for 22.8% of the site’s traffic on April 25. The previous day it had roughly 280,000 visitors.

“Way Day succeeded in driving major increases in highly engaged traffic and follows a wider trend of brands recognizing their ability to ‘create a holiday,'” says Gitit Greenberg, SimilarWeb’s senior director of marketing insights. “Wayfair’s ability to utilize this tactic with such success is indicative of the company’s growing digital prowess.”

Wayfair’s sales during the week of Way Day were up 91.2% compared to the same week a year earlier, according to data from Slice Intelligence that’s based on the email receipts of 63,108 U.S. online shoppers. The items it sold were more expensive than a year earlier as the number of items purchased grew 78.5%.

“Retail holidays have traditionally been anchored to public holidays, as shoppers needed time off from work to visit stores,” Shah said. “With the first half of the year seeing Presidents’ Day and Memorial Day as the major promotional dates in the calendar. As online has grown, the importance of these shopping events has reduced as consumers can shop at any time from the convenience of their own home. We saw Way Day as a great opportunity to bring customers a compelling promotional event at a time of year when home can be top of mind with, for example, outdoor spaces being refreshed and homes often being prepared for sale.”

Steve Conine, Wayfair co-founder and co-chairman, tells Internet Retailer that Way Day’s success speaks to the strength of the Wayfair brand. “It’s neat to see how brand has enough strength to create an artificial holiday out of nothing,” he says.