Throngs of shoppers today are expected to take up where they left off last weekend, cruising parking lots to look for empty spaces and jamming stores to take advantage of specials on merchandise.

While they don't know it, the shoppers are part of a new vanguard when it comes to the after-Christmas retailing. The last week of December and most of January, once considered a time for retailers to unload what didn't sell during the run up to Christmas, is now an increasingly important sales period as shoppers cram into stores with gift cards.

"In looking at the past couple of years, it looks like January has been beefed up with the whole gift card explosion," said Ron Yoda, general manager of Kahala Mall. "It has increased business after Christmas substantially."

Yoda's mall and Ala Moana Center are among those planning to open early today to take advantage of the post-Christmas rush. They're also planning sales promotions in January to attract the increasing number of people heading to stores. Gift card sales in the United States were expected to soar to $24.8 billion, a $6 billion increase, during the recent holiday shopping season, according to a National Retail Federation estimate. That's helped make the day after Christmas either the second or third busiest retail day during December. Meanwhile, January has risen in importance, accounting for 7.4 percent of annual sales in 2005, up from 7 percent five years earlier.

"We're happy to receive gift cards," said Kane'ohe resident Nancy Nakano, out shopping at Ala Moana last week. She said she has received several gift cards in recent years, including those for Longs Drug Stores. She usually hits the sales today.

"Since we have the gift cards, we figure let's go to Longs."

Ala Moana plans to open at 8 a.m. today, or an hour and a half earlier than normal. It's also planning a Jan. 1 early morning sales event in which 26 retailers will fill surprise bags with gift merchandise that's sold for half the package's value. Shopping center spokesman Matthew Derby said the event borrows from the "fukubukuro" promotions in Japan and is proving to be popular. He said January is forecast to be a good sales month for the center.

"We're actually looking at one of our best Januarys," Derby said. "You see a lot of gift card redemptions, and you still have a lot of people coming to the mall looking for deals and some post-holiday shopping."

Nationally, the after-Christmas period has been transformed from days when people come in to exchange an ill-fitting sweater to one where people are shopping, said George Whalin, president of San Marcos, Calif.-based Retail Management Consultants and an annual visitor to the Islands. He said because some retailers are so good at forecasting these days, they typically sell through much of their pre-Christmas inventory and don't have much left to sell in the final week of December or January.

Therefore, many retailers are now buying inventory specifically for after Christmas, he said.

"Retailers have come to actually bring in a lot of merchandise for this part of the season," Whalin said. "It goes into the second or third week of January."

The gift cards are also valued by shoppers who stash them away. Connie Durant of Washington, a former Hawai'i resident, said while shopping at Ala Moana that her family values the cards and typically takes six months to a year to use them up.

"We treat them like a treasure," Durant, 47, said while shopping with her daughter, Alex, 14. They said the cards are used to buy special treats for themselves during the year.

The Durants aren't representative of most gift-card recipients, who retailers say usually cash in their cards within the first couple of months of ownership.

Yoda said Kahala Mall hopes to get some of that spending as it opens an hour earlier at 9 a.m. today and schedules a sidewalk sale in January. He said savvy retailers have adjusted to the trend.

"The customer has gotten smarter. They know as you get closer to Christmas you're going to see sales and after Christmas you'll see sales," Yoda said. "Good retailers take advantage of that."

Reach Greg Wiles at gwiles@honoluluadvertiser.com.