What version of ConfigMgr are you running? If it is a supported version then you should be able to apply Time zone setting out of the box in the Apply Windows settings step itself. No need to declare TS variable anymore for this.
_SMSTSTimezone variable values
The _SMSTSTimezone variable stores the time zone information in the following format (without spaces):Bias, StandardBias, DaylightBias, StandardDate.wYear, wMonth, wDayOfWeek, wDay, wHour, wMinute, wSecond, wMilliseconds, DaylightDate.wYear, wMonth, wDayOfWeek, wDay, wHour, wMinute, wSecond, wMilliseconds, StandardName, DaylightNameExample
For the Eastern Time U.S. and Canada, the value would be 300,0,-60,0,11,0,1,2,0,0,0,0,3,0,2,2,0,0,0,Eastern Standard Time,Eastern Daylight Time
Can someone show me where you would find the Time Zone in this format for Central Standard? Please direct me to the doc that explains or lists all of the TZ's.