We got in touch with Vincent Fontaine from Swelen labs, who built an open source flash date slider, a la google analytics. You can see it in action in the page: http://labs.swelen.com/?p=dateslider

The .fla et .swf files are attached to this ticket.

There is some work to do (in the flash itself) before we can consider including it in Piwik, including:

• Currently, you can select any date ranges from day A to day B. Piwik doesn't offer reports on custom date ranges (see Core: Provide custom date range feature #572). we need the ability to define the type of allowed date range selection, eg. days, weeks, months or years.
• add i18n of month names below the slider
• (optional) Regarding the date compare mode (when 2 dates are selectable), we might want to have two selection boxes (eg. a blue and an orange one) to allow to select two date ranges at once on the timeline.

The remaining question is How can this be smoothly integrated within the Piwik UI?. I don't have an answer at this stage, I would let anyone interested in this new feature comment or suggest a mockup of how this could look like.

This ticket can be picked up by someone with experience in flash and UI design. Please let us know your interest in the comments and you can take over this development.