I was recently asked this question from a client and quite frankly I advised that any day is okay.

Au contraire!

I did a Google search and found a blog that writes about this specific subject. Mark Biernat says:
“Consider the day and time of posting for the biggest impact on your specific audience. You might write it another day but post it on a high volume traffic day for your blog.” And he came up with a ranking of days in descending order in which to blog:

Ranking of the days

These are the best days to post to your blog for optimal traffic in descending order.

• Thursday – this is the best day to post to your blog for a one day impact.  Many people are tired of working and just surfing the web at work. Thursday tends to me one of my highest traffic days. It has a great impact for people in their 20s, who are counting the days to the weekend. So if your target market on your website is the 20 something crowd try this day.
• Sunday – early evening is a very good day to write a blog post for personal items or even e-bay type sales. most people are at home with nothing to do waiting for their weekend to end, especially Sunday late in the afternoon. Most people are pretty depressed. I generally do not like to work on Sunday as it is against my beliefs, but often I find myself posting any way. In fact, it is Sunday morning before everyone is up and I am writing on my blog now.  I guess I justify Sunday blogging as a mix of fun and work so I classify it as a loophole.   Anyway, any topic connected to buying and selling personal items or self improvement does well, including blogging.
• Monday- This day has the impact that work web surfers have the whole week to pass it one and share something interesting.  Especially on Monday morning when people are getting adjusted to the shock of the work week.  Great for businessmen looking at financial news. Business blogs do well on Monday and Tuesday. I have noticed big market swings occur at the start of the week, not on Friday afternoons and holidays. At the start of the web, I often surfed at work, then in the last few years I had a rule no web or personal e-mail at all at work.  I tried to work and get home as soon as possible. But I think most jobs today are so boring that most people do a reasonable amount of personal e-mail and surfing.
• Tuesday and Wednesday are good days.  They are workhorse days. If you post of these days you usually get a reasonable number of hits. News and practical information does well on these days, less people surfing the web for gossip than answers to concrete useful questions.
• Friday light non- political subjects do well. People are ready to go, take time off work or leave early.  Further, the next day is Saturday so there is a lot of momentum lost as you can read about Saturday for posting to your blog, it is the worst.  People are tired of CNN and all the political nonsense. Even the politicians. Things to do on the weekend and travel type posts do well obviously.
• Saturday is the worst day to post to your blog- Everyone is either shopping, spending time with the kids at the gym or day tripping. Life is too short to spend online. Saturday is not a supper day for traffic or posting.

This particular client is a wedding/event planner, so according to the ranking, I would suggest that they blog on Sunday’s and Friday’s. For that matter, depending on the topic, any day would suffice.

On reflection, I will stand with my original statement, any day is a good to to post!

Read the entire article on when to blog.