The first conclusion we could are from the data provided by the online marketing Socialbakers is that Monday is the best day of the week if we want our Facebook post being among the 4000 most interesting posts of the day. That's because Monday is the day of the working week when less posts are generated on Facebook, just 14.8% of the posts are generated that day. As opposite, Thursday and Friday are the most active days with 16.8% and 17.1% of the posts of the week. Accordingly to that, our fans will get more posts those two days and they will have less opportunities to see our posts. Interestingly, the rate goes up from Monday to Friday, being weekend when there are less posts generated on Facebook. A priori it seems advisable to publish posts on Facebook on Monday or Tuesday.
As regards Twitter, it follows a similar trend with Monday being the day with less activity on weekdays, rising every day until the Friday that is the day concentrating the largest number of posts. But unlike Facebook, Saturday is the best day to post tweets to generate more interaction. This may be due to the fact that there is less volume of tweets and our fans prefer to share tweets generated by others than to post themselves and Monday is the worst day of the week in terms of interaction for our tweets.
Twitter and Facebook do not behave alike and is a further proof that it's best to maintain continuity in all publications instead of focusing on a particular day of the week. You would also bear in mind other factors such as the market in which your company operates and demographic information of your customers in order to decide the right time to publish your posts.