Last updated July 31, 2013. Created on December 18, 2007.
Edited by JohnAlbin, scito, kristoferaberg, Christopher James Francis Rodgers. Log in to edit this page.

During the development of Drupal 5.0, there was an effort to include a new core theme. The previous core themes were relatively old and didn’t reflect the latest best practices in Design, CSS styling, and XHTML development. Some developers wanted a striking new design for Drupal and some developers wanted Drupal to include an easy-to-extend theme.

Thus, the Zen theme was created with a flexible CSS layout rather than the table-based layout that was used by Drupal 4.7’s main theme, Blue Marine. Zen’s very basic styling was based on the Deliciously Blue Open Source Web Design.

However, after a lengthy debate, the final decision was to include only one new theme and that it was more important to have a new recognizable design (the Garland theme) than to have an easily-extendable theme. Thus, Zen became available under Drupal’s contributed themes rather than with core.

Zen 5.x-0.6
Released January 16, 2007 (the day after Drupal 5.0). This is the first widely-used version of Zen.
Zen 5.x-1.x-dev (dated May 7, 2007 and earlier)
Many improvements over 0.6, but with incomplete sub-theme support. Also widely used.
Zen 5.x-0.7
Released October 15, 2007. Same as previous -dev version, but with a laundry list of bug fixes.
Zen 5.x-0.8
Released November 29, 2007. Radical CSS layout change from previous versions. The change in CSS layout method was required to resolve several outstanding issues with the previous layout method.
Zen 5.x-1.0-beta1
Released January 6, 2008. Support for easy sub-theme creation.
Zen 5.x-1.0-beta2
Released January 29, 2008. Added features from Zengine.
Zen 5.x-1.0
Released February 14, 2008 (the day after Drupal 6.0). Bug fix of 5.x-1.0-beta2.
Zen 5.x-1.1
Released April 21, 2008. Added THEME_preprocess(), MODULE_preprocess(), and MODULE_preprocess_HOOK() functions. Also, bug fix of 5.x-1.0.
Zen 5.x-1.2
Released February 14, 2009. Added minor features, mostly bug fixes of 5.x-1.1.
Zen 6.x-1.0-beta1
Released May 14, 2008. Port of Zen to Drupal 6. Includes built-in fixes for all known Drupal 6 theming bugs.
Zen 6.x-1.0-beta2
Released May 20, 2008. Critical bug fix for PHP 4 users of 6.x-1.0-beta1.
Zen 6.x-1.0-beta3
Released September 15, 2008. Significant performance improvements. Updated tpl files. Added IE conditional stylesheets to .info file, feature to rebuild theme registry during theme development, and useful styling for status, warning, and error messages.
Zen 6.x-1.0
Released February 13, 2009. Boat load of bug fixes.
Zen 6.x-2.x-dev
A relatively-stable developer version of Zen that includes all the latest bug fixes and the latest bugs. Splits up monolithic zen.css into smaller, logical stylesheets.
Zen 7.x-3.0
Released April 5, 2011. XHTML based.
Zen 7.x-5.0
Released April 26, 2012. HMTL5, responsive, mobile-first and Sass/Compass.
Zen 7.x-5.1
Released May 18, 2012.
Zen 7.x-5.2
Released July 31, 2013. Bugfixes/features for users of 7.x-5.x-dev version.
Zen 7.x-5.3
Released July 31, 2013. Bugfixes/features for users of 7.x-5.1 version.
Zen 7.x-6.x-dev
Current development version.

Looking for support? Visit the forums, or join #drupal-support in IRC.