[Tickets #13947] Re: Calendar breaks on DST start date

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Ticket URL: https://bugs.horde.org/ticket/13947
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  Ticket             | 13947
  Updated By         | jsveiga at it.eng.br
  Summary            | Calendar breaks on DST start date
  Queue              | Kronolith
  Version            | 4.2.2
  Type               | Bug
  State              | Not A Bug
  Priority           | 2. Medium
  Milestone          |
  Patch              |
  Owners             |
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jsveiga at it.eng.br (2015-04-13 14:11) wrote:

Sorry, I failed to note that the (windows) client timezone should be  
set to a DST timezone (in my case, (UTC-3:00) Brasilia), and I'm using  
Firefox 37.0.1.

The calendar uses javascript functions from the browser, but the  
building of the calendar view is coming from Kronolith (for example  
kronolith.js, updateView for the large calendar view).

So it seems in some js implementations, date arithmetic works  
differently (one can argue if "different" is wrong or more strict),  
but Kronolith should be aware of that and deal with it.

For example, for the large month view, simply doing this:

#############
--- kronolith.js.orig   2015-04-13 10:56:33.267068678 -0300
+++ kronolith.js        2015-04-13 11:03:01.578750995 -0300
@@ -514,6 +514,7 @@
              var tbody = $('kronolith-month-body'),
                  dates = this.viewDates(date, view),
                  day = dates[0].clone();
+            day.setHours(15);

              $('kronolithCurrent')
                  .update(this.setViewTitle(date, view, data));
#################

on the updateView function where it builds the month table, solves the  
issue by moving the time away from 00:00, avoiding that adding  
days/weeks to Date results in an unexpected day due to the DST switch  
point.

Similar workarounds can be done for the other instances where DST is  
causing problems.