Index: trunk/doc/pslib/psLibSDRS.tex
===================================================================
--- trunk/doc/pslib/psLibSDRS.tex	(revision 2193)
+++ trunk/doc/pslib/psLibSDRS.tex	(revision 2194)
@@ -1,3 +1,3 @@
-%%% $Id: psLibSDRS.tex,v 1.143 2004-10-25 20:59:03 price Exp $
+%%% $Id: psLibSDRS.tex,v 1.144 2004-10-25 21:41:40 price Exp $
 \documentclass[panstarrs,spec]{panstarrs}
 
@@ -3443,18 +3443,26 @@
 
 \begin{verbatim}
-psTime *psTimeAdd(const psTime *time, psF64 delta);
-psF64 psTimeSubtract(const psTime *time, psF64 delta);
+psTime *psTimeMath(const psTime *time, psF64 delta);
 psF64 psTimeDelta(const psTime *time1, const psTime *time2);
 \end{verbatim}
-\code{psTimeAdd} adds some time to a \code{psTime}.
-\code{psTimeSubtract} subtracts two times.  \code{psTimeDelta} gives
+\code{psTimeMath} adds the \code{delta} (in seconds; may be negative)
+to a \code{psTime}.  \code{psTimeDelta} gives
 the difference between times \code{time1} and \code{time2} (which may
 be negative).
 
+Note that in both these, the difference between two times is to be
+expressed in \textit{SI} seconds, and not inclusive of leap seconds.
+For example, if we add 30 seconds to 1998-12-31T23:59:45Z, the result
+is 1999-01-01T00:00:14Z, since a leap second was introduced at
+1999-01-01T00:00:00Z.
+
 Time math may only be done on the \code{psTime} TAI type, and so the
 functions shall internally convert the \code{psTime} inputs to TAI
-before performing the math.  The type of the time returned by
-\code{psTimeAdd} and \code{psTimeSubtract} shall be the same as that
-of the input \code{time}.
+before performing the math; this is in order that leap seconds are
+accounted for.
+
+The type of the time returned by \code{psTimeMath} shall be the same
+as that of the input \code{time}.
+
 
 \subsubsection{Time Tables}