This is not a Government of Canada website
The purpose of this website is to provide a working example of the WET-BOEW-GCWeb theme created by TNG Consulting Inc. together with the Government of Canada for Moodle software . Demo courses are only available in English however multi-language courses are supported.
Understanding Moodle Release Cycles
Since Moodle 2.7 (LTS), Moodle has been released on a time-based schedule. If new features are not ready, they get pushed back to the next release. There are weekly, bi-monthly, biannual and LTS releases of Moodle.
Weekly - These are very minor releases, so small that they are simply identified by a + symbol after the version number (e.g. 3.5.1+). They contain recently added bug and security fixes. Although Moodle has an excellent quality assurance process, these fixes don't necessarily have real-world testing yet. No new features are ever included which makes it very likely to remain compatible with your existing plugins and therefore an easy upgrade. That said, if there is a bug or security issue in your current version of Moodle which is addressed in one of these weekly releases, it would be worth upgrading. Otherwise, I recommend waiting for the bi-monthly updates.
Bi-monthly (minor release) - These official releases for Moodle - that come out in January, March, May, July, September, November - contain all of the accumulated weekly fixes from the past 2 months. This changes the last digits in the version number (e.g. from 3.5.0 to 3.5.1). By this time fixes have been in use, probably pretty well tested in the real world and are usually pretty safe. They don't tend to include new features added unless absolutely necessary which makes these releases very likely to remain compatible with your existing plugins and therefore an easy upgrade.
Biannual (major release) - These are the official releases of Moodle that come out in May and November each year. They increment the "3.5" part of the version number (e.g. 3.4 to 3.5). These releases get a lot more quality assurance testing thanks to hundreds of volunteers from around the world. Anyone is welcome to participate. New features and major changes are typically introduced in these releases of Moodle.
Because of this, more caution and additional effort should be applied when upgrading to these releases including ensuring that all your plugins, themes and courses are compatible. If they aren't, you need to get in touch with the developer / maintainer of those theme and plugins to encourage them to make their code compatible. Because it is all open source, you can sometimes accelerate the process by offering financial support or fixing the issues yourself and sharing the fixes back with the developer. Sometimes plugins and themes may not require any changes and will work fine however only your own testing will be able to determine this. You would definitely want to do this on a separate test copy of your website so that it doesn't affect active learners on your current Moodle site.
Note that a change from Moodle 3.9 to 4.0 would be no more of a leap than Moodle 3.4 to 3.5. Think of this part of the version number as if there was no decimal point between the 3 and the 5. In fact, Moodle 3.5 is actually referred to as Moodle 35 in its source code which is why Moodle 4.0 (40) will come after 3.9 (39).
All major releases of Moodle will continue to receive bug fixes for 12 months and 18 months of security fixes as of the date of their initial release. The only exception is for LTS releases (see below).
Did you know? Moodle adopted a biannual release schedule to accommodate educational institutions on both sides of the world. For example, in Australia, summer vacation is in December/January where in other parts of the world it is in July and August. It is also why Learn Moodle Basics is offered within a few months after each major release.
LTS (Long Term Support release) - This is a special version of Moodle which comes out every 2 years and is specifically geared toward those who don't have the resources to upgrade every 6 months. Every 4th major release gets to be one of these - like Moodle 2.7, 3.1 and 3.5. The next LTS release, Moodle 3.9, will come out in May 2020. What is special about LTS releases? They receive security fixes for 36 months instead of just the usual 18 months giving them a longer lifespan.
All of this is only of any value if you also plan on updating Moodle regularly. The only reason you might want to upgrade to a newer release of Moodle in between LTS releases would be if there was one or more particular new features that you absolutely had to have or if you were just starting out with Moodle. Then plan on upgrading to the next LTS release and synchronize your upgrade cycle with LTS releases.
If LTS releases are supported for 3 years, why do they come out every 2 years? Regardless of whether a major release is an LTS or not, when they first come out, theme and plugin developers might need time to catch up. In some cases, 3rd party developers may decide to stop supporting a theme or plugin and you will need to come up with an alternative plan. Your organization will also likely need time to setup a test site, do lots of testing and address any compatibility issues. You may even need time to change-up things and take advantage of new features. The extra year gives your team time to work all of the issues out while still maintaining a safe production Moodle environment.
I believe that it is important to understand not only what's new in each release of Moodle but also be aware of its release cycle so that you can come up with a sustainable plan to maintain your Moodle site. If you are interested in a high level list of changes, I recently updated the Moodle page on Wikipedia where you will find a summary of the major changes from Moodle 3.1 to 3.5. What it does not mention are the hundreds of bug and security fixes included in each major release of Moodle. More details are available in the Moodle 3.5 release notes. At the bottom of the page, there is a link to Release notes for Moodle 3.4. To find out what's new since a particular release, continue to follow these links for each release until you get to your current version.