fix calendar across timezone, showEnd/FullDay

[sdetweil]

Please make sure that you have followed these 4 rules before submitting your Pull Request:

1. Base your pull requests against the develop branch.

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2. Include these infos in the description:

timezone correction for repeating events (RRULE) with wrong date, right time, correction used offset hours, not day hours) (#2623)
if showEnd and FullDate format specified together showEnd result was overlayed (#2629), add else clause

• Does the pull request solve a related issue?
  Fixes: Calendar: end date missing for multi day events (like holidays) (followup to #2529) #2629 Calendar-Module: Timezone calculation #2632

[codecov-commenter]

Codecov Report

Merging #2748 (c5ed70d) into develop (bd5664c) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop    #2748   +/-   ##
========================================
  Coverage    69.08%   69.08%           
========================================
  Files            8        8           
  Lines          262      262           
========================================
  Hits           181      181           
  Misses          81       81           

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