Time is important. Keeping accurate time has been one of the major challenges of technology throughout all of history. Here’s a little history lesson from the US Navy:
In 1845, at the request of the Secretary of the Navy, the Observatory installed a time ball atop the 9.6-inch telescope dome. The time ball was dropped every day precisely at Noon, enabling the inhabitants of Washington to set their timepieces. Ships in the Potomac River could also set their clocks before putting to sea. The Observatory’s Time Service was initiated in 1865. A time signal was transmitted via telegraph lines to the Navy Department, and also activated the Washington fire bells at 0700, 1200, and 1800.
For the Navy, time is important for navigating all those ships around the globe. For Sprout Social, time is important because we have some pretty cool technology that determines the optimal time to send a tweet or Facebook post to get the most reach for our customers.
Time in the Browser
Daylight Savings and Olson Files
# US central time, represented by Chicago # Alabama, Arkansas, Florida panhandle (Bay, Calhoun, Escambia, # Gulf, Holmes, Jackson, Okaloosa, Santa Rosa, Walton, and # Washington counties), Illinois, western Indiana # (Gibson, Jasper, Lake, LaPorte, Newton, Porter, Posey, Spencer, # Vanderburgh, and Warrick counties), Iowa, most of Kansas, western # Kentucky, Louisiana, Minnesota, Mississippi, Missouri, eastern # Nebraska, eastern North Dakota, Oklahoma, eastern South Dakota, # western Tennessee, most of Texas, Wisconsin # Rule NAME FROM TO TYPE IN ON AT SAVE LETTER Rule Chicago 1920 only - Jun 13 2:00 1:00 D Rule Chicago 1920 1921 - Oct lastSun 2:00 0 S Rule Chicago 1921 only - Mar lastSun 2:00 1:00 D Rule Chicago 1922 1966 - Apr lastSun 2:00 1:00 D Rule Chicago 1922 1954 - Sep lastSun 2:00 0 S Rule Chicago 1955 1966 - Oct lastSun 2:00 0 S
It turns out, there is a group of files that keep a record of all the daylight savings rules across the world just for this kind of thing:
The tz database, also called the zoneinfo database or IANA Time Zone Database, is a collaborative compilation of information about the world’s time zones, primarily intended for use with computer programs and operating systems. It is sometimes referred to as the Olson database after the founding contributor Arthur David Olson.
Walltime makes it easy to convert from one UTC date to the “wall time” of just about any time zone:
var someUTCDate = new Date(), chicagoWallTime = WallTime.UTCToWallTime(someUTCDate, "America/Chicago"), backToUTCTIme = WallTime.WallTimeToUTC("America/Chicago", chicagoWallTime);
In addition, what if we need to convert from a local time zone time in another time zone than your own to a UTC time? We’ve got you covered there too:
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