A month ago, Chile was two hours ahead of eastern time. Three weeks ago, Chile was one hour ahead. Now Chile and the East Coast are on the same time, which is where they will stay until October rolls around. Being on the same time makes sense: Santiago is at roughly the same longitude as Boston. If you slid the whole country of Chile straight up on a map, it would end up right around Martha’s Vineyard and Nantucket (to put Chile’s length in perspective, if the northern tip of Chile touched Massachusetts, the southern tip would pass Florida, Cuba, all of the Caribbean, and land smack in the middle of Venezuela).
The explanation for this two hour, one hour, no hour difference? As a rule of thumb, confusion about time is usually due to either Einstein’s theories of relativity or daylight savings time. The Chile situation is due to the latter. In the U.S., time “springs” an hour ahead in the spring and “falls” an hour behind in the fall. Chile applies the same rules to its clocks, but since it lies in a different hemisphere, the U.S.’s spring is Chile’s fall and vice-versa. For a sizable portion of the year, Chile and the East coast share a timezone. In the fall, around the time the U.S. clocks fall back, Chile’s spring ahead, creating the two-hour gap. Chile’s clocks return to normal a few weeks before the U.S.’s, which explains the temporary one-hour disparity.
For more daylight savings information, consult your friendly Wikipedia. By comparison, Einstein’s theories are pretty simple.