Use the EDCLLOCL job to change the C/C++ locale time information for your site.

Recommendation: Do not install this usermod. The default C/C++ locale (EDC$S370) will by default obtain the time zone difference from Greenwich mean time from the system. If your C/C++ application requires a different time zone other than the one obtained from the system, you can use the tzset() and the TZ environment variable described in z/OS XL C/C++ Runtime Library Reference.