Built into every blogging software is the ability to include the date of when you are posting the blog entry. Usually this appears somewhere at the top of the post near or next to the byline. Many blogging systems actually include the date as part of the URL structure too. For example, this Daily Golden Nugget includes /2013/06/05/ to indicate June 5, 2013.
If I wanted to I could hide the dates in my Daily Nuggets, but honestly, the topics I write about are ever-changing and my readers need to know when they were written. The Nugget I wrote back on August 25, 2010 is completely invalid today because GoWalla, the subject of the Nugget, is out of business. Someone might mistake that post as new and relevant information if I didn't include the date.
On the other hand, there are times when the information you write about will be valid forever. Do you think anyone will ever invalidate the 4C's of Diamonds? What about the chemical composition of diamonds? Probably not, so that type of information is good to post without an associated date.
Anything you can post up to your website forever is actually referred to as "evergreen content." Like an evergreen tree which stays green through 4 seasons of the year, this type of website information will be valid no matter when you read it.
Evergreen content tends to be more applicable to some industries and not others. Science and research website are good examples, but from what I see in my measured results I find that the all retail industries are far too competitive and they cannot rely on highly ranked evergreen content.
As of today, and this could change tomorrow since this Nugget is certainly NOT evergreen, Google will rank their SERPs in order of freshness. In other words, the most relevant and recent content is listed first. Google has ways to figure out which website pages are new and which ones have been hanging around for a while.
On the day your website went live you might have published the best engagement story ever, and you consider it to be timeless and evergreen. Sadly, all it takes to knock you out of top ranking is for a competitor down the street could publish a new engagement story on their website with today's date. From what I see in the jewelry industry, dated blog posts always trump evergreen blog posts.
Another affect I'm noticing is how users perceive your website when you don't include a date on a post. Website users are starting to understand that new information matters more than old and they don't want to be stuck using old information when an entire world of new information should be available on their smartphones.
A few weeks ago a friends-of-a-friend on Facebook were morning the "recent" loss of pin-up legend Bettie Paige. Early one morning, an entire thread popped up based on one persons comment on her death and the article was shared four times by noon with dozens of comment per post. Sadly this was just an example of mis-tagged evergreen content since Bettie Paige passed away in 2008, and not in May 2013. No one wants to look like a fool when talking to their friends about "current" information they read off the internet--um, because everything you read on the internet is true, right? This is doubly true when people post weeks old political news and friends and family jump on the helpless poster on how wrong they are, now that recent data shows otherwise!
So when it comes to blogging on your website, don't hide your posting dates. Display them proudly and even include them in your URL structure.
There might be a few of you out there that worry that your customers will see that you don't update your blog often, and to you I say... Update your blog more often.