Generally speaking, from both an SEO and user experience point of view, it is indeed good practice to include a date tag or stamp at the top of a blog post, as it helps the reader understand the context and also builds trust.
To be clear, I am referring to a physical indication of the publication date on the page itself – not included in the URL of the post.
Context
Content creators may write with a different perspective depending on the context of what else was happening at a particular time. Therefore having a date stamp will help the reader to understand why a certain perspective was taken.
This context becomes even more pivotal when the topic is technical or advice-based. For example, we’ve all read an article about how to achieve a task on a mobile device, only to find the solution no longer works as there have been subsequent software updates. Not only is this a waste of time, but it can also leave the reader feeling frustrated with the brand or organisation that provided it.
Without a date tag, it’s impossible to tell if an article was written two days or two years ago and therefore whether it is at all useful to the reader.
Trust
Including the date in a blog post, is really key to building audience trust. It’s one of those things that readers don’t notice until it’s not there and could increase a site’s bounce rate if readers immediately take against the lack of transparency.
In fact, date stamps are often pulled through into SERPs results so by not including a date tag, a site may not benefit from the click-through at all, as the searcher selects results that are more obviously written within a timescale that they consider reasonable for a particular topic.
So why doesn’t everyone use date tags?
Apart from the few who just haven’t considered it, the main reason seems to be that of evergreen content and the concern that this carefully-curated timeless material will become less valuable or even redundant if it is time-stamped.
Although there is no data to actually prove this, the general consensus in the SEO community is that the trust and transparency accrued by a date stamp far outweighs the potential harm done by no date stamp at all.
But as Google favours sites that are regularly updated with fresh content, it is an understandable concern of webmasters that older evergreen content with a date stamp could lose its value over time.
In which case, feel free to update it.
How to update blog content
In general, it’s better to update an existing piece of content than recreate it. Competing content isn’t helpful to search engines and can cannibalise search traffic, so if the topic is still relevant then updating the blog post is usually the best way to go.
This strategy is best adopted with evergreen pieces of content that performed really well in the past and need a nudge in the right direction to remain that way.
Typically, the writer will adjust the time stamp and then in the article header or footer state the date the article was originally published.
Publishers and those who are in the business of news, tend to have a CMS that includes both the original date and subsequent updates but most blog posts will only be designed to include the former. Therefore it’s best to update the date tag and then mention the original publication date elsewhere in the copy, otherwise the original date will continue to show in SERPs.
The date stamp doesn’t need adjusting for every single tiny update (for example if the organisation changed name or the odd statistics here and there) but should be used for more meaningful revisions.
This also applies if, over time, a site has created several pieces of similar content which would all be better combined into one. With redirects in place, and a better-optimised page that isn’t competing with itself, it’s not unusual to see the new post outperform the combination of its predecessors as the link juice from all the pages boosts the new single destination.
Date tags and stamps aren’t directly connected to rankings and traffic generation but all arrows definitely point in the direction that dated content has the propensity to outperform non-dated stamped copy.