Make comparison and subtraction of aware objects ignore tzinfo if the
operands have identical tzinfo members (meaning object identity -- "is").
I misunderstood the intent here, reading wrong conclusion into
conflicting clues.
diff --git a/Doc/lib/libdatetime.tex b/Doc/lib/libdatetime.tex
index 1adbc8e..32c0f93 100644
--- a/Doc/lib/libdatetime.tex
+++ b/Doc/lib/libdatetime.tex
@@ -863,10 +863,15 @@
\begin{itemize}
\item
- comparison of \class{timetz} to timetz, where timetz1 is considered
- less than timetz2 when timetz1 precedes timetz2 in time, and
- where the \class{timetz} objects are first adjusted by subtracting
- their UTC offsets (obtained from \method{utcoffset()}).
+ comparison of \class{timetz} to \class{time} or \class{timetz},
+ where \var{a} is considered less than \var{b} when \var{a} precedes
+ \var{b} in time. If one comparand is naive and the other is aware,
+ \exception{TypeError} is raised. If both comparands are aware, and
+ have the same \member{tzinfo} member, the common \member{tzinfo}
+ member is ignored and the base times are compared. If both
+ comparands are aware and have different \member{tzinfo} members,
+ the comparands are first adjusted by subtracting their UTC offsets
+ (obtained from \code{self.utcoffset()}).
\item
hash, use as dict key
@@ -1011,11 +1016,13 @@
\item
datetimetz1 + timedelta -> datetimetz2
timedelta + datetimetz1 -> datetimetz2
+
The same as addition of \class{datetime} objects, except that
datetimetz2.tzinfo is set to datetimetz1.tzinfo.
\item
datetimetz1 - timedelta -> datetimetz2
+
The same as addition of \class{datetime} objects, except that
datetimetz2.tzinfo is set to datetimetz1.tzinfo.
@@ -1025,32 +1032,31 @@
\naive\_datetimetz1 - datetime2 -> timedelta
datetime1 - \naive\_datetimetz2 -> timedelta
- \item
- Subtraction of a \class{datetime} or datetimetz, from a
+ Subtraction of a \class{datetime} or \class{datetimetz}, from a
\class{datetime} or \class{datetimetz}, is defined only if both
- operands are \naive, or if both are aware. If one is aware and
- the other is \naive, \exception{TypeError} is raised.
+ operands are \naive, or if both are aware. If one is aware and the
+ other is \naive, \exception{TypeError} is raised.
- \item
- If both are \naive, subtraction acts as for \class{datetime}
- subtraction.
+ If both are \naive, or both are aware and have the same \member{tzinfo}
+ member, subtraction acts as for \class{datetime} subtraction.
- \item
- If both are aware \class{datetimetz} objects, a-b acts as if a and b were
- first converted to UTC datetimes (by subtracting \code{a.utcoffset()}
- minutes from a, and \code{b.utcoffset()} minutes from b), and then doing
+ If both are aware and have different \member{tzinfo} members,
+ \code{a-b} acts as if \var{a} and \var{b} were first converted to UTC
+ datetimes (by subtracting \code{a.utcoffset()} minutes from \var{a},
+ and \code{b.utcoffset()} minutes from \var{b}), and then doing
\class{datetime} subtraction, except that the implementation never
overflows.
\item
- Comparison of \class{datetimetz} to \class{datetime} or datetimetz. As for
- subtraction, comparison is defined only if both operands are
- \naive\ or both are aware. If both are \naive, comparison is as
- for \class{datetime} objects with the same date and time components.
- If both are aware, comparison acts as if both were converted to
- UTC datetimes first, except the the implementation never
- overflows. If one comparand is \naive\ and the other aware,
- \exception{TypeError} is raised.
+ comparison of \class{datetimetz} to \class{datetime} or
+ \class{datetimetz}, where \var{a} is considered less than \var{b}
+ when \var{a} precedes \var{b} in time. If one comparand is naive and
+ the other is aware, \exception{TypeError} is raised. If both
+ comparands are aware, and have the same \member{tzinfo} member,
+ the common \member{tzinfo} member is ignored and the base datetimes
+ are compared. If both comparands are aware and have different
+ \member{tzinfo} members, the comparands are first adjusted by
+ subtracting their UTC offsets (obtained from \code{self.utcoffset()}).
\item
hash, use as dict key