What time or day do people talk about libraries, or visit them?
According to this it is unsurprisingly every day during general opening hours, with a slight preference for the middle of the week rather than later.
Scott Golder of Cornell University has created a way of determinng what people (on Twitter) are doing or saying at what time. This is done by running chosen text against a data set of millions of time coded Twitter messages. Go see http://timeu.se