A Visual History of System Preferences
Early versions of OS X until 10.3 included a favorites bar at the top where users could drag and drop their favorite settings. In 10.4, this was removed and replaced with the search feature that highlights matching icons as you type a query.
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In the first OS X Public Beta, a shade drawn over a window represented Energy Saver. Before release, the now recognizable light bulb took its place.
Over the years, the icon has represented the most efficient light bulb technology of the time. So, in 10.5, the icon changed from an incandescent bulb to a more efficient compact fluorescent. Then, in 10.10, the light bulb changed again to an LED design.
Via Nick Heer:
I particularly appreciated this explanation of the two different dates often seen in Apple’s calendar-related icons[…]
Previously:
Update (2020-09-28): Ken Harris:
You can see exactly the moment in 2013 when @Apple said “fuck it, I’m just gonna make this text GRAY” and then “oh yeah? HOLD MY BEER”