master 16e16e1f8c: Improve documentation of `posn-timestamp'

[Po Lu]

branch: master
commit 16e16e1f8c1001fca6597bf0efb61e236d935628
Author: Po Lu <luangruo@yahoo.com>
Commit: Po Lu <luangruo@yahoo.com>

    Improve documentation of `posn-timestamp'
    
    * doc/lispref/commands.texi (Accessing Mouse): Improve
    documentation of `posn-timestamp' by actually describing the
    timestamp it returns.
---
 doc/lispref/commands.texi | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/doc/lispref/commands.texi b/doc/lispref/commands.texi
index e37f600243..a8ce294ad9 100644
--- a/doc/lispref/commands.texi
+++ b/doc/lispref/commands.texi
@@ -2701,7 +2701,10 @@ the character at that position.
 @cindex timestamp of a mouse event
 @defun posn-timestamp position
 Return the timestamp in @var{position}.  This is the time at which the
-event occurred, in milliseconds.
+event occurred, in milliseconds.  Such a timestamp is reported
+relative to an arbitrary starting time that varies according to the
+window system in use.  On the X Window System, for example, it is the
+number of miliseconds since the X server was started.
 @end defun
 
   These functions compute a position list given particular buffer