[mythtv-commits] Ticket #9676: Obtaining program times across daylight savings time change gives inaccurate results

[MythTV]

#9676: Obtaining program times across daylight savings time change gives
inaccurate results
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 Reporter:  mythtv@…                |           Type:  Patch - Bug Fix
   Status:  new                     |       Priority:  minor
Milestone:  unknown                 |      Component:  MythTV - General
  Version:  0.24-fixes              |       Severity:  medium
 Keywords:                          |  Ticket locked:  0
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 This bug affects users having a TimeOffset set to 'Auto'. I can testify
 that it affects schedulesdirect data, but it would apply to any listing
 service that lists using UTC time.

 The bug is that in the days leading up to a daylight savings time change,
 when mythfilldatabase obtains program information for a day after the
 daylight savings time change will have occurred, the time of that program
 is calculated incorrectly. By the time the time change actually happens,
 your program guide has roughly two weeks of incorrect data loaded into it.
 The workaround is to wait until the time changes, clear out that data, and
 do a new mythfilldatabase.

 The  bug is in the MythSecsTo utility function, because it calculates the
 time difference independently of the day, and thus can't take into account
 the hour lost or gained across a daylight savings change.


 I will attach a patch that addresses the problem. This simple program
 demonstrates the problem for CST or other time zones that changed local
 time on March 13 this year:

 {{{
 #include <iostream>

 #include <util.h>

 using namespace std;

 int main(int argc, char** argv) {
   // this range should only cover a 23-hour period, due to the time change
 in
   // the middle of it
   QDateTime before = QDateTime(QDate(2011,3,12), QTime(23, 00, 00));
   QDateTime after = QDateTime(QDate(2011,3,13), QTime(23, 00, 00));

   cout << MythSecsTo(before,after) / 60 / 60
        << " vs " << before.secsTo(after) /60 / 60
        << "\n";;
 }
 }}}


 I hope this is not a dup - I searched for tickets, and although some were
 in the neighborhood none seemed completely like this issue. Apologies if I
 missed the right ticket.

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Ticket URL: <http://code.mythtv.org/trac/ticket/9676>
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