Most Important Retail Holidays

Buyers expect aggressive promotions, free shipping and lots of offers on retail holidays.  Don't miss the sales opportunity.

Halloween 

eBay's guide to sell products on Halloween http://for-business.ebay.com/aggressive-retailing-and-three-phases-halloween

Black Friday

Online merchants can take advantage of both Black Friday and Cyber Monday
Cyber Monday

Christmas

During the biggest retail reason of the year, eBay offers free holiday sale seminar, and hot best seller list providing guidance on how to capture sales.

There are subcategories of Christmas merchandise as well: stocking stuffers and white elephant gifts. These gifts are generally smaller,  less expensive, and more creative. 

Less obvious retail holidays

Flags, team uniforms sell well during World Cup and also Independence Day. 

Memorabilia, sports uniforms, and collectibles sell well after a winning final championship of sports teams.

Is summer a holiday? Yes and No! It's a holiday for kids. And it is followed by back-to-school. It is a season change, and another opportunities. Google teaches you how to make summer sales https://www.thinkwithgoogle.com/articles/bbq-to-burns-summer-trends.html
Summer is also a good time for juice, smoothie and cocktails.