Wal-Mart is kicking off its deals two hours earlier than last year, with the first round of bargains rolling out at 6 p.m. on Thanksgiving, the next at 8 p.m. and yet another at 8 a.m. on Friday. Target said most stores will stay open from 8 p.m. on Thursday for 27 hours straight; last year, the deals began flowing at 9 p..m.

Toys R Us said shoppers can come in for 29 consecutive hours starting at 5 p.m. on Thanksgiving. Old Navy's "unprecedented" 29-hour run will start at 9 a.m. on Thanksgiving, shut down at 4 p.m. and then pick up from 7 p.m. until midnight the next day. Kmart's 41-hour marathon launches at 6 a.m. on Nov. 28.

For much of the past year, retail sales have been dour, battered by volatile weather, shaky consumer confidence, ramifications of the government shutdown and looming costs related to the new federal healthcare law.

And the shortest holiday season since 2002 will only make shopping more nerve-racking for retailers. With only 27 days between Thanksgiving and Christmas — six fewer than last year — stores can expect to lose $1.5 billion in potential sales, according to a report this month from Adobe Digital Index.

Last year, more than 35 million Americans hit up retailers and websites on Thanksgiving, up from 29 million the previous year, according to the National Retail Federation.

"People are shopping earlier and earlier every year," said David Kuntz, an analyst with Standard & Poor's. "I wouldn't be surprised at all if stores are very crowded on Thanksgiving."

Some shoppers justify the spending sprees as a "social and recreational activity," a way to spend time with family out on the town, Kuntz said. Others, accustomed to the 24-hour availability of online merchandise, are increasingly demanding the same of traditional stores, he said.

Many retailers aren't even waiting for Thanksgiving as they try to snatch early holiday shoppers. Kmart aired its first Christmas ad in September. Several merchants unveiled their hot holiday lists before summer was over.

Some analysts are skeptical that Thursday openings will give retailers the sales boost they want.

"It's clearly going to diminish Black Friday's importance and siphon out sales," said Retail Metrics' Perkins. "But just because they're open on Thanksgiving doesn't mean they're drawing in a larger portion of sales — it's just being spread out over several days instead of being highly concentrated on one."

tiffany.hsu@latimes.com

Twitter: @tiffhsulatimes