Time zone calculations

[meagvg]

I'm practicing rally planning and routing with Basecamp. My routine Basecamp planning is done on the Mac version. Because of rally data spreadsheet exports I need to use BC on Windows.
With rally planning, the arrival/departure timing is important.
I've run simple test routes and found that the BC Mac will calculate the correct time zone changes. But the Windows version doesn't. I need to manually change arrival times in a route that crosses US time zones.
I'm wondering if I've missed a setting in the Windows version. I actually prefer the Windows BC for a few reasons and find it hard to believe Garmin fixed time zones on Mac but not on Windows.
Any suggestions or advice is really appreciated.