http://d.puremagic.com/issues/show_bug.cgi?id=3741

           Summary: std.date YearFromTime broken or very slow
           Product: D
           Version: 1.055
          Platform: x86
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Phobos
        AssignedTo: nobody@puremagic.com
        ReportedBy: steve.teale@britseyeview.com


--- Comment #0 from Steve Teale <steve.teale@britseyeview.com> 2010-01-25 04:57:11 PST ---
YearFromTime is used in several places in std.date.  If you run:

import std.stdio;
import std.date;
import std.c.linux.linux;

extern(C) int clock();

void main()
{
   int t1 = clock();
   int y;
   for (int i = 0; i < 100000; i++)
   {
      long t = getUTCtime();
      y = YearFromTime(t);
   }
   int t2 = clock();
   writefln("y = %d", y);
   writefln("elapsed %d", t2-t1);
   t1 = clock();
   for (int i = 0; i < 100000; i++)
   {
      int tt = time(null);
      tm *ptm = gmtime(&tt);
      y = ptm.tm_year+1900;
   }
   t2 = clock();
   writefln("y = %d", y);
   writefln("elapsed %d", t2-t1);
}

You will find that YearFromTime takes like 80 times longer. What's more calling localtime gets you all the other stuff too.

It looks like it is approximating the year then doing some iterations to check/adjust it, but the iterations are actually doing the whole job.

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Andrej Mitrovic <andrej.mitrovich@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |andrej.mitrovich@gmail.com
         Resolution|                            |FIXED


--- Comment #1 from Andrej Mitrovic <andrej.mitrovich@gmail.com> 2011-05-24 21:28:15 PDT ---
You can now use std.datetime.SysTime.year, as recommended in the "Migrating from std.date to std.datetime" article that will be up on DPL.org soon.

import std.datetime;
auto year = (cast(DateTime)Clock.currTime()).year;

It takes 128 microseconds on my machine. Hope that's fast enough. Otherwise file a bug report for std.datetime.

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Andrej Mitrovic <andrej.mitrovich@gmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Resolution|FIXED                       |


--- Comment #2 from Andrej Mitrovic <andrej.mitrovich@gmail.com> 2011-05-25 07:22:22 PDT ---
My mistake, this is D1. Reopened.

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