UPS posted a $1.1 billion profit for the third quarter and announced it plans to hire 55,000 seasonal employees to prepare for the busy holiday season.

The company plans to hire seasonal employees as drivers, helpers, package sorters, loaders and unloaders. The Sandy Springs-based shipping giant said that on Dec. 16, its peak day, it expects to pick up more than 34 million packages around the world.

The September quarter profit came on strong domestic business and improving global economic forecasts, UPS said. Net income amounted to $1.16 in diluted earnings per share, up from a $469 million profit, or 48 cents a share, a year ago. However, last year’s results involved a $559 million charge for pension restructuring.

Total revenue was $13.5 billion for the third quarter, up 3.4 percent from the same period of 2012.

Looking forward, UPS said it expects to benefit from robust online sales for the holiday, forecasting an 8 percent increase in daily volume during the peak season.

Because of a late Thanksgiving, this year’s shopping period between Black Friday and Christmas is the shortest since 2002. That could generate more revenue from express shipments, but could also bring challenges if bad weather disrupts operations at the company’s air hub in Louisville.

Chief financial officer Kurt Kuehn said the Affordable Care Act will cost UPS more than $100 million, including the requirement to cover dependents up to the age of 26 and the $63 transitional reinsurance fee employers must pay for each person covered. That fee is to help defray the cost to insure high-risk people in the individual market.

UPS told its workers earlier this year that it is dropping coverage for about 15,000 of 33,000 spouses of nonunion employees in the U.S. — if those spouses can obtain insurance from their own employers.

Meanwhile, the company continues efforts to negotiate labor contracts with the Teamsters union after workers rejected some agreements in June and the company reached agreements to extend existing contracts.

Since then, some supplemental agreements have been approved, but other supplemental agreements and a UPS Freight contract must still be negotiated.