Develop a time zone event publishing widget

We would like to publish training events to the global audience within different time zones. We will be publishing the date and time in our time zone in London, and would like to have a little widget next to it that will display the time in the web visitor's time zone. It MUST recognise the fact that many time zones have Daylight Saving Time (DST) and there are several different kind of DST worldwide. The good thing is that this website [login to view URL] recognise all these and they offer an API. We would need someone to develop this little widget using their API. To be more flexible, we would want the widget to detect the user's time zone setting and display time correctly, then followed by a dropdown to allow them to change the time zone in case their time zone setting is wrong, or they want to attend the event from a different time zone. I hope this makes sense. We use Joomla site, but it doesn't have to be in the form of a Joomla extension.