Refer reader to platform library docs for specific semantics.
Resolves SF bugs 697989, 697988, 697986.
diff --git a/Doc/lib/libtime.tex b/Doc/lib/libtime.tex
index f68f452..a6a2e73 100644
--- a/Doc/lib/libtime.tex
+++ b/Doc/lib/libtime.tex
@@ -5,9 +5,12 @@
\modulesynopsis{Time access and conversions.}
-This module provides various time-related functions.
-It is always available, but not all functions are available
-on all platforms.
+This module provides various time-related functions. It is always
+available, but not all functions are available on all platforms. Most
+of the functions defined in this module call platform C library
+functions with the same name. It may sometimes be helpful to consult
+the platform documentation, because the semantics of these functions
+varies among platforms.
An explanation of some terminology and conventions is in order.