When you run an application that uses the SystemTimeToTzSpecificLocalTime function in certain Windows installations, the application performance is very poor
Assume that you develop an application by using the SystemTimeToTzSpecificLocalTime function. The application converts Coordinated Universal Time (UTC) to the specified time zone’s corresponding local time. However, when you run the application on some Microsoft Windows operating systems, the application’s performance is very poor.
For more information on this issue, including potential causes, workarounds, and resolutions, see: Microsoft KB Article KB960417.