by: John Koetsier | VentureBeat.com

There are good times to start social media marketing campaigns, and there are absolutely horrible why-on-earth-would-you-choose-that times. How’s a savvy online marketer to know which is which?

YesMail Interactive ran a comprehensive three-month study of consumer social engagement with online campaigns for 20 major retails brands, including Abercrombie & Fitch, The Gap, Ralph Lauren, American Eagle, J Crew, and Forever 21. It discovered some astonishing insights which it’s sharing with the world … such as why Tuesday is such a great day to kick off a campaign.