Statistically, Impossible to predict but for most cases, Monday and Friday.
Most companies generally publish news in the second half of Friday to Sunday mid noon. It affects the shares as well as the forex industry as it induces a lot of volatility.
Like tomorrow 13–10–2016 you can see volatility in terms of volume in Indian Stock Market because markets were closed for the last two days keeping a sheer tension. Watch over the stocks of TCS becauseTCS Q2 Results: No fireworks expected; net profit seen down 0.2% QoQ – The Economic Times which is although is a bad result but is a good result to me as all other IT companies are suffering from post-brexit loss of revenues. So, I may Buy after waiting for first two hours of opening tomorrow!
Here is how I have had researched on volumes using our great Google Sheets
So it is a statistical proof that day doesn’t triggers anything at all. It is random but based on above data I may assume for the case of TCS, we see less volatility in Thursday. The main objective of all this hassle is I was trying to find a data driven approach.