It was on that date, four weeks after a gathering in Chicago called the General Time Convention, that Standard Railroad Time was created, in a commercial co-optation of the clock whose echoes can be felt today, high above Park Avenue in Manhattan, on the sixth floor of Grand Central Terminal. There, at the top of two ladders and tucked away behind the terminal’s operations center, is a cramped brick room that contains the greasy innards of a hundred-year-old clock with a stained-glass dial, the largest of Grand Central’s noteworthy timepieces.

“The New York Central Railroad knew it couldn’t run the system back then without time zones,” said Dan Brucker, a spokesman for Metro-North Railroad. “So they petitioned Congress.” And eventually, with the passage of the Standard Time Act in 1918, the railroads’ time zones were essentially enacted into law.

http://www.nytimes.com/2009/09/17/nyregion/17rooms.html?_r=1&hp