When promoting your self-published book, the social media tool Twitter ought to play an important role in the marketing strategy. Knowing when to tweet, however, can maximize your efforts.

According to a number of studies, the best time to tweet is Monday through Thursdays from 1 to 3 p.m.

That’s because more people are on Twitter during Monday through Thursday between 9 a.m.-3 p.m. with usage increasing until peaking between 1-3 p.m.

Of course, these times are relative. If your business is national, you need to tweet over a longer spread of time than 1-3 p.m. in your time zone, or you’ll miss the peak times in other parts of the country. For example, if your business is based in Chicago (Central Time), you would aim messages for the East Coast at noon-2 p.m. Central Time and messages for the West Coast at 3-5 p.m. Central Time.

Add a photo as well to your tweet. Tweets with photos see a 36% increase in clicks over those tweets without a picture. If that’s not enough to convince you, tweets with photos also see a 41% increase in retweets, 31% increase in visits, 48% increase in favorites, 33% increase in visitor-to-lead conversion rate, and a 55% increase in leads, compared to those tweets that are just text.

The absolute worst time to tweet is Friday after 3 p.m. and Saturday through Thursday after 8 p.m. Though people are on Twitter during this time, the number of users drops considerably compared to the earlier mentioned peak hours.