Using some animated clocks from d3 to show the difference between how US and EU timezone transitions work.
The top row shows three clocks in the three main European Union timezones on the last Sunday in October. As London passes 0200 BST it resets to 0100 GMT; simultaneously, the clocks change in Berlin and Helsinki.
The bottom row shows four clocks for the US timezones, on the first Sunday in November. In contrast to the EU clocks, the DST ripples across the country at 0200 local time.
(Thanks to bl.ocks.org/tomgp/6475678 for the starting point and to @mbostock for help with heights.)