Sorry if the extended downtime today interfered with your plans to solve problems. As some of you know, 2038 marks the end of the Unix timestamp. So with 2038 fast approaching (; a large back end update was carried out today to shift all of the internal time/date DB values from Unix timestamps to DateTime objects. This has taken a number of weeks to modify all of the scripts on my local machine to handle the new DateTime objects throughout the site. It has also required significant changes to the DB tables.

I have done as much testing as possible to ensure that everything is working but until the site undergoes extensive use, it is unlikely that I will have covered all possible interactions. If you notice any issues, I would be very grateful if you took the time to report the issue at the alternative forum: https://projecteuler.chat/viewtopic.php?t=8026

I wish the changes today brought something more exciting, but it was a necessary change. So I would like to thank you for your patience and be assured have already begun thinking about how to handle the end of DateTime objects at the end of year 9999.

The technological world has changed beyond our wildest imaginations in recent years with the widespread access to generative artificial intelligence tools. Whereas this is mostly for the good, a small number of members have possibly been using it inadvertently in a manner that conflicts with the mission of Project Euler. So as to be absolutely clear, we have added some additional guidelines that can be found in our Generative Artificial Intelligence Tools Policy.

For most members, it will be business as usual, but there are a tiny minority of members that might need to review how they have been solving problems when it comes to competing for places in the public tables and any materials posted in the problem threads.

We really hope that you appreciate our efforts and we will update the policy as and when it becomes necessary to ensure that it aims to protect the integrity of everything we do here.

Members have always had the option of making their accounts private, which means they will not appear in any public ranked tables, including the fastest solver tables. However, we have now provided an option which allows members to maintain public status, but opt out of individual fastest solver tables. If you have earned a place in any table, by viewing that table you will see a link at the end of the row containing your username which allows you to opt out of that particular table. Please be aware that opting out is permanent, so you will be asked to confirm your choice before it is completed.

To ensure consistency in relation to privacy options, and to simplify the whole process, a change has been made to how accounts with private status are now handled. This change only impacts the fastest solvers tables. If the account is private, any problems solved during this time will automatically be opted out to reduce the burden of performing this task manually each time.

However, an important change to be aware of is that the choice of switching accounts from public to private now will automatically opt you out of all previously solved problems.

Please note that if your account is currently private, no changes have been made to your previous problems at this stage. However, if you would like to take advantage of this more robust privacy option, you can switch to public and back to private again.

These changes are made clear on your Account page in the section where you can make your account private, where it explains the consequence of switching between public and private. In addition, the privacy policy has been updated to reflect these changes.

We hope that the flexibility of the new opt out feature and the simplification of what it means to have a private account is clearer and more helpful for everyone.

The guide to formatting posts has always asked members to use single dollar for inline TeX content and double dollar for block level, but some alternatives were previously supported. For example, it was possible to use \[ and \] delimiters for block level and you were able to add TeX to the page directly by using \begin{...} \end{...}. However, this put a burden on the JavaScript module that processes the MathJax because it had to scan the entire page to render content. Consequently, support for the alternative delimiters has been removed.

Due to the way that the new BBCode module parses posts, TeX content is now served directly to the MathJax module, so this should make pages load quicker and put less burden on client browsers. In addition, restricting the delimiters to single dollar and double dollar enables the posts to be more stable as content is strictly processed as TeX.

Rather than just turn off the alternatives and leave posts broken, I have done my best to convert existing posts to handle the new required format with some degree of automation. But please be aware that I had to manually oversee more than one-thousand posts over several days, so there may be some of those posts that are not displaying as expected any longer. I would ask members who used the alternative methods to be vigilant and if you get the chance, please check over your own posts to ensure they are viewing correctly.

I realise this might be frustrating for those who have been using the alternative methods, but I hope that you appreciate the attempt to make the forum more robust and easier to use for everyone.

Over the years the BBCode module used in the problem threads has continued to be modified and have additional tags added. So, to ensure a more streamlined performance, the entire module has been rewritten. Every attempt has been made to support both recent and legacy posts and I have tried my best to check the rendering is accurate on multiple posts. But it is quite possible that I might have missed something. If you have identified an issue, please report it at the designated thread on the alternative forum: BBCode Update 2025

I have added a few new tags and tidied up the way some of the existing tags are used. Check out About... Forum Tags for more information.

In addition, these changes have had a knock-on effect with how the syntax highlighter operates. So if you spot something not quite right, please report it at the thread above. As a small bonus, it is now possible to switch the syntax highlighting stylesheet from your Account page. The default, and the one we have been using for many years, is Stack Overflow, but you can also use GitHub and Google, which all support light (default) and dark mode.