IBM X-Force Kassel analyzed billions of spam messages gathered by its spam honeypots from December 2016 to June 2017. Researchers found more than 83 percent of spam was sent on weekdays, with Tuesday showing the most activity, followed by Wednesday and Thursday. The majority of the activity stops around 8pm UTC, or 4pm EST, for spammers targeting U.S. spammers in Europe, India, and South America were more likely to follow a consistent workday schedule, where activity was high during the day while North American spammers had constant activity throughout the day.”]
Source: https://www.csoonline.com/article/3199997/don-t-like-mondays-neither-do-attackers.html