DST maybe? http://en.wikipedia.org/wiki/Daylight_saving_time
"Then on March 19, 1918, the U.S. Congress established several time
zones (which were already in use by railroads and most cities since
1883) and made daylight saving time official (which went into
effect on March 31)"
On Feb 28, 2006, at 3:06 PM, Ben Kazez wrote:
I have an application that retrieves an NSCalendarDate from a .ics
file and adds one year to it until the date is within a certain
range. (This isn't the most efficient way to do things, but it's
fast enough for my needs.) This algorithm runs into a problem with
dates before 1919. Here's the line that adds the date components:
currentExpandedDate = [[IEPSystemCalendar
dateByAddingComponents:frequency toDate:currentExpandedDate
options:0] dateWithCalendarFormat:BKWebScriptCalendarFormat
timeZone:[[unexpandedEvent objectForKey:@"DTSTART"] timeZone]];
The frequency variable is set to one year using -[NSDateComponents
setYear:]. As an example, here the app is starting with 1914-03-01
00:00:00 -0600:
March 01, 1915 00:00:00
March 01, 1916 00:00:00
March 01, 1917 00:00:00
March 01, 1918 00:00:00
March 01, 1919 01:00:00
March 01, 1920 01:00:00
...
(Sorry for the inconsistent date formatting.) As you can see,
after 1918, the date is one hour off. Does anyone know why this is
happening?
Ben
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