From f4160c363b7e1bc8ad47a6c00d02c0856a3be17b Mon Sep 17 00:00:00 2001
From: Otto Winter <otto@otto-winter.com>
Date: Fri, 14 Jun 2019 12:35:14 +0200
Subject: [PATCH] Fix russia timezone detection (#637)

Fixes https://github.com/esphome/issues/issues/378#issuecomment-500219634
---
 esphome/components/time/__init__.py | 31 ++++++++++++++++++-----------
 1 file changed, 19 insertions(+), 12 deletions(-)

diff --git a/esphome/components/time/__init__.py b/esphome/components/time/__init__.py
index 8c85a3d62f..634de26f00 100644
--- a/esphome/components/time/__init__.py
+++ b/esphome/components/time/__init__.py
@@ -52,6 +52,15 @@ def _tz_dst_str(dt):
                                  _tz_timedelta(td))
 
 
+def _non_dst_tz(tz, dt):
+    tzname = tz.tzname(dt)
+    utcoffset = tz.utcoffset(dt)
+    _LOGGER.info("Detected timezone '%s' with UTC offset %s",
+                 tzname, _tz_timedelta(utcoffset))
+    tzbase = '{}{}'.format(tzname, _tz_timedelta(-1 * utcoffset))
+    return tzbase
+
+
 def convert_tz(pytz_obj):
     tz = pytz_obj
 
@@ -59,24 +68,14 @@ def convert_tz(pytz_obj):
     first_january = datetime.datetime(year=now.year, month=1, day=1)
 
     if not isinstance(tz, pytz.tzinfo.DstTzInfo):
-        tzname = tz.tzname(first_january)
-        utcoffset = tz.utcoffset(first_january)
-        _LOGGER.info("Detected timezone '%s' with UTC offset %s",
-                     tzname, _tz_timedelta(utcoffset))
-        tzbase = '{}{}'.format(tzname, _tz_timedelta(-1 * utcoffset))
-        return tzbase
+        return _non_dst_tz(tz, first_january)
 
     # pylint: disable=protected-access
     transition_times = tz._utc_transition_times
     transition_info = tz._transition_info
     idx = max(0, bisect.bisect_right(transition_times, now))
     if idx >= len(transition_times):
-        tzname = tz.tzname(now)
-        utcoffset = tz.utcoffset(now)
-        _LOGGER.info("Detected timezone '%s' with UTC offset %s",
-                     tzname, _tz_timedelta(utcoffset))
-        tzbase = '{}{}'.format(tzname, _tz_timedelta(-1 * utcoffset))
-        return tzbase
+        return _non_dst_tz(tz, now)
 
     idx1, idx2 = idx, idx + 1
     dstoffset1 = transition_info[idx1][1]
@@ -84,6 +83,14 @@ def convert_tz(pytz_obj):
         # Normalize to 1 being DST on
         idx1, idx2 = idx + 1, idx + 2
 
+    if idx2 >= len(transition_times):
+        return _non_dst_tz(tz, now)
+
+    if transition_times[idx2].year > now.year + 1:
+        # Next transition is scheduled after this year
+        # Probably a scheduler timezone change.
+        return _non_dst_tz(tz, now)
+
     utcoffset_on, _, tzname_on = transition_info[idx1]
     utcoffset_off, _, tzname_off = transition_info[idx2]
     dst_begins_utc = transition_times[idx1]