Labor Day—which was Sept. 3 this year—generated $2.08 billion in online sales in the U.S., according to Adobe Digital Insights data.

This is the first one-day holiday to surpass $2 billion in online spending in the U.S., outside of the November-December holiday shopping season, according to Adobe data, which is based on 1 trillion visits to more than 4,500 retail sites and 55 million SKUs.

Here is how Labor Day ranks among other one-day shopping events within the last 12 months:

Labor Day sales grew 23.4% over 2017, when shoppers spent $1.69 billion online, according to Adobe. The analytics vendor attributes the high growth to discounts on high-priced product categories, such as electronics, appliances and home and garden.

Adobe also notes that email drove 30.1% of sales on Labor Day, the highest of any channel that Adobe tracks for last-touch attribution. The next were:

60.9% of Labor Day 2018’s sales came from desktops, 28.4% from smartphones and 10.7% on tablets. Smartphone’s share of sales is higher than what Adobe found for the 2017 holiday season, where smartphones generated 23% of online sales, tablets 10% and desktop 67%, between Nov. 1 and Dec. 31.

Retailers should take note of smartphones’ growing share of sales, says Costa Lasiy, an Adobe analyst. 

“We saw a strong correlation between how well a retailer did on Labor Day and how well they did during the holiday season last year,” Lasiy says.

Labor Day comes at the end of back-to-school shopping season, which also had a stellar online shopping period, Adobe finds. Consumers spent $58.1 billion online during back-to-school season, which Adobe defines as July 23-Sept 5. Adobe’s estimate is based on all online spending during this period and not just back-to-school-specific sales.

Internet Retailer estimates that back-to-school sales reached $23.432 billion online, which includes only back-to-school specific sales for kindergarten through college students between July 1-Sept. 15.

For Adobe’s back-to-school season estimates, smartphones’ share of sales during this period was lower than Labor Day 2018, but higher than last holiday season:

• 25.0% of back-to-school season sales were via smartphones, totaling $14.5 billion
• 8.8% via tablets, totaling $5.1 billion
• 66.2% via desktops, totaling $38.5 billion

Desktops still account for the largest share of online sales and highest average ticket at $142, as well as largest conversion rate at 3.37% for back-to-school season sales, according to Adobe. Tablets had a 2.34% conversion rate with a $125 basket size, and smartphones had a 1.24% conversion rate with a $111 average basket size.

E-commerce platform provider Shopify Inc. also identified Labor Day as one of the top back-to-school shopping days, based on aggregated data from 600,000 retailers. The Friday before Labor Day weekend was also a peak shopping day for Shopify merchants, and both Friday, Aug. 31, and Labor Day, Sept. 3, brought in $130 million each day on Shopify sites.

To read more about back-to-school online sales and other peak seasons throughout the calendar year, check back for Internet Retailer’s soon-to-be-released Peak Seasons report.