display-world-time does not work on Windows.

diff --git a/etc/PROBLEMS b/etc/PROBLEMS
index 72e5a7a..76753c3 100644 (file)
--- a/etc/PROBLEMS
+++ b/etc/PROBLEMS
@@ -2198,6 +2198,13 @@ month names with consistent widths for some locales on some versions
 of Windows. This is caused by a deficiency in the underlying system
 library function.
 
+The functions set-time-zone-rule, and display-time-world (which uses it)
+do not work on Windows. Fixing this is difficult, since Windows uses
+localtime for the system clock, and any attempt to change the timezone
+would have to be accompanied by a clock change for the results to remain
+consistent. The way in which these functions are used is not intended to
+cause such system-wide disruption.
+
 Files larger than 4GB cause overflow in the size (represented as a
 32-bit integer) reported by `file-attributes'.  This affects Dired as
 well, since the Windows port uses a Lisp emulation of `ls' that relies