(LATIMES) — Upset by more store openings on Thanksgiving Day, shoppers and retail employees are stepping up efforts to get big chains to back off.

Black Friday, the day after Thanksgiving, has long been considered the start of the holiday shopping season, with retailers offering big discounts and early-morning deals to attract hordes of shoppers.

But opening times have been drifting earlier. Chains such as Wal-Mart and Sears have announced plans for Black Friday events this year starting as early as 8 p.m. Thanksgiving Day. Frustrated workers and customers say they are unhappy about cutting their family Thanksgiving dinners short.

More than 20 petitions on Change.org urge stores to open later.

Note: Read our discussion guidelines before commenting.