This isn't a ksh feature, it is standard behavior required for any shell conforming to the POSIX standards or the Single UNIX Specifications. But, the format shown above is not correct. A valid setting for TZ will include at least the zone's name and offset from UTC. The normal setting for Texas in the United States would be TZ=CST6CDT (not TZ=CDT) and TZ=UTC happens to work because the offset from UTC to UTC is 0, but the output from the commands:

Code:

TZ=CDT date
TZ=UTC date

will be identical except for the difference in the time zone name. Compare the results above with:

Code:

TZ=CST6CDT date

where you'll see a 6 hour difference in time (this time of year) as well as a difference in the time zone name. The output from the above three commands should be something like:

Code:

Thu Dec 12 00:17:50 UTC 2013
Thu Dec 12 00:17:50 UTC 2013
Wed Dec 11 18:17:50 CST 2013