tzset — Print POSIX-compatible timezone ID from current Windows timezone setting
tzset  [ -h  |   -V ]
Options:
  -h, --help               output usage information and exit.
  -V, --version            output version information and exit.
      Use tzset to set your TZ variable. In POSIX-compatible shells like bash, dash, mksh, or zsh:
export TZ=$(tzset)
      In csh-compatible shells like tcsh:
setenv TZ `tzset`
      
The tzset tool reads the current timezone from Windows and generates a POSIX-compatible timezone information for the TZ environment variable from that information. That's all there is to it. For the way how to use it, see the above usage information.