将 GMT 日期时间转换为本地时间 [英] Convert GMT datetime to local

问题描述

我有一个 GMT 时区的日期时间值.如何将其转换为我的本地时区?我希望有一个功能.请注意，由于夏季，我不能只是添加或减去差异.例如，该函数可以这样工作:

I have a datetime value in GMT timezone. How can I convert it to my local timezone? I would expect there to be a function for this. Please note that I can not just add or subtract the difference, because of the summertime. For example the function could work like this:

data _null_;
  gmtdatetime="17SEP14:09:42:10"dt;
  localdatetime=tz2local(gmtdatetime,"GMT");
run;

我尝试了一些格式和信息的组合，但没有成功:

I tried some combinations of formats and informats without luck:

data _null_;
  gmtdatetime="17SEP14:09:42:10"dt;
  a=put(gmtdatetime,E8601DZ20.0);*Converts the value to "2014-09-17T09:42:10Z" to indicate that it is GMT;
  localdatetime=input(a,B8601DT.);*Reads the GMT value;
  put localdatetime datetime.;*This still prints the value as the original GMT value...;
run;

谢谢，斯蒂格

推荐答案

我做了一个返回 GMT 偏移量的函数，但是当我编译它时，我得到这个错误:

I made a function that would return the GMT offset, but when I compiled it, I got this error:

ERROR: Built-in SAS FUNCTION or SUBROUTINE already exists with name 'GMToff'.

事实证明，SAS 中有一个未记录的函数返回 GMT 偏移量，幸运的是我选择了相同的名称！此处是一些用法示例.无论如何，它不会像我想要的那样返回特定时间的偏移量，仅针对当前时间.这是一个将日期时间转换为本地"时间的函数，给定一个时区(仅支持 GMT，但根据需要添加额外的时区应该是微不足道的):

It turns out, there is an undocumented function in SAS that returns the GMT offset and by luck I chose the same name! Here are some examples of usage. Anyways, it will not return the offset on a specific time, as I wanted, only for the current time. Here is a function that will convert the datetime to "local" time, given a timezone (only supports GMT, but adding additional timezones as needed should be trivial):

proc fcmp outlib = Apfmtlib.funksjoner.localtime;
function localtime(datetime,tz$);
    if upcase(tz)="GMT" then do;
      offset_normal=3600;
      offset_summer=7200;
    end;
    localtime=datetime+offset_normal;
    /*If datetime is between 1 AM the last Sunday of March and 1 AM the last Sunday of October it is "summertime" in central Europe:*/
    if intnx('week',mdy(3,31,year(datepart(datetime))),0)*86400 + 3600 le datetime le intnx('week',mdy(10,31,year(datepart(datetime))),0)*86400 + 3600 then localtime=datetime+offset_summer;;
    return(localtime);
endsub;
quit;
options cmplib = Apfmtlib.funksjoner;
/*Usage examples:*/
data _null_;
    gmtdatetime="17SEP14:09:42:10"dt;
    localdatetime=localtime(gmtdatetime,"GMT");
    put localdatetime datetime.;
    gmtdatetime="17DEC14:09:42:10"dt;
    localdatetime=localtime(gmtdatetime,"GMT");
    put localdatetime datetime.;
run;

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