# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1269821145 -7200
# Node ID 962e330c8c1003e1fd96c08a686a951f4a13ab32
# Parent  eee0f0ee7c2378b5ab7606606340739ac8cb0f1d
Introduced a default UTC conversion for Olson-based local times, choosing the
time in the zone preceding any zone change in a regime.
Added release notes.

diff -r eee0f0ee7c23 -r 962e330c8c10 EventAggregatorSupport.py
--- a/EventAggregatorSupport.py	Mon Mar 22 23:56:39 2010 +0100
+++ b/EventAggregatorSupport.py	Mon Mar 29 02:05:45 2010 +0200
@@ -1033,6 +1033,8 @@
             date = self.as_date()
 
             # Add the minutes and hours.
+            # NOTE: This makes various assumptions and probably would not work
+            # NOTE: for general arithmetic.
 
             minute += minutes
             if minute < 0:
@@ -1083,6 +1085,17 @@
             minutes = int(match.group("minutes") or 0) * sign
             return hours, minutes
 
+        # Attempt to handle Olson time zone identifiers.
+
+        dt = self.as_olson_datetime()
+        if dt:
+            seconds = dt.utcoffset().seconds
+            hours = seconds / 3600
+            minutes = (seconds % 3600) / 60
+            return hours, minutes
+
+        # Otherwise return None.
+
         return None
 
     def olson_identifier(self):
@@ -1101,18 +1114,61 @@
         else:
             return None
 
+    def _as_olson_datetime(self, hours=None):
+
+        """
+        Return a Python datetime object for this datetime interpreted using any
+        Olson time zone identifier and the given 'hours' offset, raising one of
+        the pytz exceptions in case of ambiguity.
+        """
+
+        olson = self.olson_identifier()
+        if olson and pytz:
+            tz = pytz.timezone(olson)
+            data = self.padded().as_tuple()[:6]
+            dt = datetime.datetime(*data)
+
+            # With an hours offset, find a time probably in a previously
+            # applicable time zone.
+
+            if hours is not None:
+                td = datetime.timedelta(0, hours * 3600)
+                dt += td
+
+            ldt = tz.localize(dt, None)
+
+            # With an hours offset, adjust the time to define it within the
+            # previously applicable time zone but at the presumably intended
+            # position.
+
+            if hours is not None:
+                ldt -= td
+
+            return ldt
+        else:
+            return None
+
+    def as_olson_datetime(self):
+
+        """
+        Return a Python datetime object for this datetime interpreted using any
+        Olson time zone identifier, choosing the time from the zone before the
+        period of ambiguity.
+        """
+
+        try:
+            return self._as_olson_datetime()
+        except (pytz.UnknownTimeZoneError, pytz.AmbiguousTimeError):
+            return self._as_olson_datetime(-1)
+
     def ambiguous(self):
 
         "Return whether the time is local and ambiguous."
 
-        olson = self.olson_identifier()
-        if olson and pytz:
-            try:
-                tz = pytz.timezone(olson)
-                data = self.padded().as_tuple()[:6]
-                dt = tz.localize(datetime.datetime(*data), None)
-            except (pytz.UnknownTimeZoneError, pytz.AmbiguousTimeError):
-                return 1
+        try:
+            self._as_olson_datetime()
+        except (pytz.UnknownTimeZoneError, pytz.AmbiguousTimeError):
+            return 1
 
         return 0
 
diff -r eee0f0ee7c23 -r 962e330c8c10 README.txt
--- a/README.txt	Mon Mar 22 23:56:39 2010 +0100
+++ b/README.txt	Mon Mar 29 02:05:45 2010 +0200
@@ -26,6 +26,13 @@
 Important Notices
 -----------------
 
+In release 0.6, support for event times has been introduced. Due to the
+complicated nature of times, time zones, time regimes, and so on, the
+behaviour of the software may change in future versions to support common
+use-cases in a more convenient fashion. Please be aware that implicitly chosen
+or generated time or time zone information may change for events, particularly
+those whose times are ambiguous or ill-defined.
+
 In release 0.5, the "download this calendar" and "subscribe to this calendar"
 links have been fixed to return only events within the specified period and to
 work with day- and month-relative calendars. Users who have bookmarks in their
@@ -213,7 +220,8 @@
     replace the link information provided by the RSS and iCalendar summaries.
   * Fixed the production of the summaries when pages with no available edit
     log information are to be included.
-  * Added support for event times and time zone/regime information.
+  * Added support for event times and time zone/regime information. This is
+    subject to revision.
 
 New in EventAggregator 0.5 (Changes since EventAggregator 0.4)
 --------------------------------------------------------------