The autumn sales season in the retail sector will be from November 1 to November 10, according to recent legal amendments.
Traders agreed with the government earlier this year that there would be four periods of sales per year.
As a result of the autumn sales, stores will be open on Sunday, November 3.
The decline in Greek retail sales accelerated in July from the previous month, data released last month showed.
Retail sales by volume fell 14.0 percent year-on-year after a revised 8.0 percent drop in June. It was the biggest drop in three months.
Hit by the country's deep economic slump and record unemployment, retail sales by volume fell 12 percent in 2012, bringing the sector's total contraction in 2009-2012 to 34 percent.