Microsoft
First published on TECHNET on Mar 07, 2007
Q: Our VC++ studio 6.0 application uses _timezone variable. Where does it get that value from? From the system clock or msvcrt.dll?
A: Environment variables are provided by the parent process, which includes system-wide settings. Also, a process can change its own environment block using the following functions:  _tzset(), _putenv(), _wputenv(), _putenv_s(), _wputenv_s(), SetEnvironmentVariable()