Craft Time Diff brings in the Twig Date Extension.

• Place the timediff folder inside your craft/plugins/ folder.
• Go to settings/plugins and install timediff

The plugin adds the Twig time_diff filter (http://twig.sensiolabs.org/doc/extensions/date.html).

Renders the difference between a date and now:

{{ post.published_at|time_diff }}

Outputs "1 day ago" or "in 5 months"

Need to translate into other languages? Version 1.1 adds a simplistic delimited string that can be split into an array, and uses Craft's built-in translation string where available:

{{ post.published_at|time_diff_array }}

Outputs "past|1|day|singular" or "future|5|month|plural"

This could then be turned into an array with Twig's split filter:

{% set diffArray = post.published_at|time_diff_array|split('|') %}

The array's first element will be either the word "past" or "future" (not translated), the second element is the number of units, the third is the unit name (translated if available), and the last is the word "plural" or "singular".

• SensioLabs for writing the Date Extension