2.1. DST

Daylight Savings Time (DST), sometimes called ‘Summer Time’, is the period during the course of a year in which a particular geopolitical region advances its local time by one hour compared to the standard time for that region (as determined by its ‘timezone’). The goal is to better match hours of work and school to real daylight hours during the course of a day, for better productivity and potential energy savings.

For a more complete description and a history of DST, see http://en.wikipedia.org/wiki/Daylight_savings_time.