Curiously, South America – well, Argentina and Chile at any rate – appear to operate on the same time zone.  At the latitude of their capital cities, the continent is right at 15 degrees of longitude wide and, so, it makes sense they’d use the same time.  Without politics and national borders, all time zones would be a uniform 15 degrees of longitude wide because it takes the sun 1 hour to move 15 degrees across the sky (360/15 = 24).  For us, it means that there will never be a time zone change throughout the Southern Cone program.

This makes it easier to discuss time differences to the United States.  I live in the Eastern Time Zone while my parents live in Central.  That’s a simple one hour difference so if it is 11pm at my house, it’s 10pm at theirs.  Moreover, we live at the same latitude so when it’s summer at my house, it’s summer at theirs.

Santiago is about 100 km (60 miles) east of the west coast of South America.  So, you might think, it’s well west of the east coast of the United States.


Take a look at a World Map or, better, a globe.  Santiago, on the WEST side of South America, is about 10 degrees of longitude EAST of my home in North Carolina.  It is, more or less, straight south of Cape Cod.  Buenos Aires is 12 degrees further east.

In North American winter, Buenos Aires and Santiago are on daylight savings time what with it being summer there and all (more on this in a later post).  That will switch as North America enters summer and South America winter.  However, the switch won’t happen at the same time which leads to the table below.

Location:                  South America              Winston-Salem              OK/TX

until March 12                  3:00                                   1:00                          12:00

March 12 to May 15         3:00                                   2:00                           1:00

May 15 to return              3:00                                   3:00                           2:00


This table is a result of the United States starting Daylight Savings Time far sooner than is warranted astronomically.  North America will begin DST on March 12 while South America is still using it.  North America will spring ahead, an hour toward South America, on March 12.  South America will terminate it’s DST on May 15, falling back an hour and pulling even with North America’s Eastern Time Zone.

It makes sense for Santiago and Cape Cod to be on the same time.  Time – real time, that is, not the fake stuff Congress churns out – is measured by following the sun.  Local noon is when the sun is at its highest point in the sky.  If you’re at 70 degrees west longitude that happens at the same instant no matter what your latitude is.  However, how high the sun in most definitely depends on your latitude.

I’m going to the southern hemisphere so you can expect to read a lot about the effect of latitude on the apparent altitude of celestial objects.  But, for now, rest easy knowing you can figure out what time it is where I am so long as you know where you are.


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