Port some of the base system to FreeBSD. Extracted from...

base/third_party/nspr/prtime.cc

 /* Portions are Copyright (C) 2007 Google Inc */
 /* ***** BEGIN LICENSE BLOCK *****
  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
  *
  * The contents of this file are subject to the Mozilla Public License Version
  * 1.1 (the "License"); you may not use this file except in compliance with
  * the License. You may obtain a copy of the License at
  * http://www.mozilla.org/MPL/
  *
  * Software distributed under the License is distributed on an "AS IS" basis,
@@ skipping 131 matching lines @@
     // convert to microseconds which is what PRTime expects.
     CFAbsoluteTime absolute_time = 
         CFGregorianDateGetAbsoluteTime(gregorian_date, NULL);
     PRTime result = static_cast<PRTime>(absolute_time);
     result -= exploded->tm_params.tp_gmt_offset +
               exploded->tm_params.tp_dst_offset;
     result += kCFAbsoluteTimeIntervalSince1970;  // PRTime epoch is 1970
     result *= kSecondsToMicroseconds;
     result += exploded->tm_usec;
     return result;
-#elif defined(OS_LINUX)
+#elif defined(OS_LINUX) || defined(OS_FREEBSD)
     struct tm exp_tm = {0};
     exp_tm.tm_sec  = exploded->tm_sec;
     exp_tm.tm_min  = exploded->tm_min;
     exp_tm.tm_hour = exploded->tm_hour;
     exp_tm.tm_mday = exploded->tm_mday;
     exp_tm.tm_mon  = exploded->tm_month;
     exp_tm.tm_year = exploded->tm_year - 1900;
 
     time_t absolute_time = timegm(&exp_tm);
 
@@ skipping 1031 matching lines @@
                               + 60 * localTime.tm_hour
                               + 1440 * (localTime.tm_mday - 2);
         }
 
   result->tm_params.tp_gmt_offset = zone_offset * 60;
   result->tm_params.tp_dst_offset = dst_offset * 60;
 
   *result_imploded = PR_ImplodeTime(result);
   return PR_SUCCESS;
 }