用纬度/经度计算出时间？ [英] Figure out time by latitude/longitude?

问题描述

这是协议。我有一个位置的纬度/经度设置。我需要弄清楚当前时间是在那个位置。这是我之前得到它的方式：

  NSDateFormatter * theFormatter = [[NSDateFormatter alloc] init]; 
 [theFormatter setDateFormat：@h：mm a]; 
 NSDate * todaysdate = [NSDate date]; 
 NSString * todaysDate = [theFormatter stringFromDate：todaysdate]; 
 [theFormatter release]; 
  

但是，我意识到这将给用户当前位置的时间。是否有一个API在某个地方给我基于lat / lon对的时间？

提前感谢。

解决方案

不幸的是，时区（一般的时间）从来没有你想要的那么简单。

可以遵循jer的建议。经度范围从-180到180度，一天有24小时，所以你得到每个时区15度的经度。在0度经度中心这些时区，因此UTC从-7.5延伸到7.5，UTC + 1从7.5到22.5，UTC-1从-7.5到-22.5，依此类推。然后你会有一个非常简单的，错误的，如何使用时区的模型。

看看这个时区地图。

• 时区不好排序; UTC-1中的区域与UTC-3中的区域相邻。


• UTC-9.5，UTC-4.5，UTC + 3.5，UTC + 5.75和UTC +




一旦你完成了整理，你就可以开始考虑夏令时。




Here's the deal. I have a latitude/longitude set of a location. I need to figure out what the current time is in that location. Here's how I was getting it before:

NSDateFormatter *theFormatter = [[NSDateFormatter alloc] init];
[theFormatter setDateFormat:@"h:mm a"];
NSDate *todaysdate = [NSDate date];
NSString *todaysDate = [theFormatter stringFromDate:todaysdate];
[theFormatter release];

However, I realized that this will give the time for the user's current location. Is there an API somewhere that gives me the time based off of a lat/lon pair?

Thanks in advance.

解决方案

Unfortunately timezones (and time in general) is never as simple as you would like.

For a simple approximation you can follow jer's suggestion. Longitude ranges from -180 to 180 degrees, there are 24 hours in a day, so you get 15 degrees of longitude per time zone. Center those time zones on 0 degrees longitude so UTC extends from -7.5 to 7.5, UTC+1 is from 7.5 to 22.5, UTC-1 is from -7.5 to -22.5, and so on. You would then have a very simplistic, and wrong, model of how we use time zones.

Take a look at this map of time zones.

• Time zones are not well ordered; regions in UTC-1 are adjacent to regions in UTC-3.
• UTC-9.5, UTC-4.5, UTC+3.5, UTC+5.75, and UTC+13 are all valid time zones and actively in use.

Once you get that sorted out then you can start to consider daylight savings time.

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