从日期和时区计算 tm_isdst [英] Calculate tm_isdst from date and timezone

问题描述

当我跑线时

time.strptime("2012-06-01 12:00:00 "+time.strftime("%Z"), "%Y-%m-%d %H:%M:%S%Z")

它为我创建了一个结构，但标志 tm_isdst 是错误的.6 月初 DST 处于活动状态，但无论我输入什么日期，tm_isdst 标志始终设置为它现在在 localtime() 中的值.我需要知道 DST 在我输入的日期是否有效.

解决方案

首先，不要在你的格式中包含 time.strftime('%Z').您告诉它您当前的 GMT 偏移量(包括关闭夏令时)，并且 [可能] 使用它来设置 tm_isdst.

没有它，你应该得到一个带有 tm_isdst=-1 的结构:

<预><代码>>>>time1 = time.strptime("2012-06-01 12:00:00", "%Y-%m-%d %H:%M:%S")>>>时间 1time.struct_time(tm_year=2012, tm_mon=6, tm_mday=1, tm_hour=12, tm_min=0,tm_sec=0, tm_wday=4, tm_yday=153, tm_isdst=-1)

现在，您可以将它传递给 mktime，它会在给定 -1 值的情况下猜测"DST 值(我将猜测"放在引号中，因为它总是正确的，除了模棱两可的凌晨 2 点案例).这将以 time() 格式给出绝对时间.

<预><代码>>>>time.mktime([previous value]) # 我的时区是美国东部1338566400.0

然后你可以用这个值调用localtime，它会有一个正确设置的DST标志:

<预><代码>>>>time.localtime(1338566400).tm_isdst1

您也可以跳过 strptime 步骤，直接将值传递给 mktime:

<预><代码>>>>time.mktime((2012,6,1,12,0,0,-1,-1,-1))1338566400.0

When I run the line

time.strptime("2012-06-01 12:00:00 "+time.strftime("%Z"), "%Y-%m-%d %H:%M:%S %Z")

it creates a struct for me but the flag tm_isdst is wrong. At the first of June DST was active but no matter what date I enter the tm_isdst flag is always set to what it is in localtime() right now. I need to know if DST was active or not on the date I enter.

解决方案

First of all, don't include time.strftime('%Z') in your format. You're telling it your current GMT offset (including daylight saving being off) and it's [probably] using that to set tm_isdst.

Without that, you should get a struct with tm_isdst=-1:

>>> time1 = time.strptime("2012-06-01 12:00:00", "%Y-%m-%d %H:%M:%S")
>>> time1
time.struct_time(tm_year=2012, tm_mon=6, tm_mday=1, tm_hour=12, tm_min=0,
tm_sec=0, tm_wday=4, tm_yday=153, tm_isdst=-1)

Now, you can pass that to mktime, which will, given the -1 value, "guess" the DST value (I put "guess" in quotes because it will always be correct except for ambiguous 2AM cases). This will give the absolute time in time() format.

>>> time.mktime([previous value]) # my timezone is US Eastern
1338566400.0

Then you can call localtime with this value, and it will have a correctly set DST flag:

>>> time.localtime(1338566400).tm_isdst
1

You can also skip the strptime step and directly pass the values to mktime:

>>> time.mktime((2012,6,1,12,0,0,-1,-1,-1))
1338566400.0

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