fix: handle timezones with no transitions properly

[SebastianKrupinski]

Resolves: #6476

Testing: See issue ticket for details.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 23.48%. Comparing base (9d1688c) to head (991402f).
Report is 30 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #6478      +/-   ##
============================================
+ Coverage     23.47%   23.48%   +0.01%     
- Complexity      453      454       +1     
============================================
  Files           247      247              
  Lines         11712    11711       -1     
  Branches       2222     2223       +1     
============================================
+ Hits           2749     2750       +1     
+ Misses         8643     8641       -2     
  Partials        320      320              

Flag	Coverage Δ
javascript	15.05% <ø> (-0.01%)	⬇️
php	59.44% <ø> (+0.12%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[miaulalala]

Can you elaborate why skipping the first (or 0 position) solves the issue please? 🙏

[SebastianKrupinski]

Can you elaborate why skipping the first (or 0 position) solves the issue please? 🙏

Morning, sure,

This code actually process the first position, instead of skipping it, the original code, skipped transition 0, which in certain time zones is needed for time zones with static transitions.

Here is a example of how Mexico City time zone was being generated:

Before:

BEGIN:VTIMEZONE
TZID:America/Mexico_City
X-MICROSOFT-CDO-TZID:37
END:VTIMEZONE

After:

BEGIN:VTIMEZONE
TZID:America/Mexico_City
X-MICROSOFT-CDO-TZID:37

BEGIN:STANDARD
TZOFFSETFROM:-0600
TZOFFSETTO:-0600
TZNAME:CST
DTSTART:19700101T000000
END:STANDARD

END:VTIMEZONE

The Mexico City timezone has a single static transition which was being skipped originally, and because the "BEGIN:STANDARD" was missing the timezone was never applied to the event, showing the event off by the amount of the timezone offset.

[st3iny]

Tested and works.

[st3iny]

Feels a bit weird to use 1970-01-01 here.

Using $trans['time'] would also work but it can stay as is. It will be equivalent to the requested start date (one year back).

[SebastianKrupinski]

Yes, I know it looks odd, but this is how all the other software I have tested handles this, so I thought it would be best stay with the follow. The start year an date does not really matter for static time zones.

[st3iny]

Makes sense!

[SebastianKrupinski]

/backport to stable4.7

[st3iny]

/backport to stable5.0