fix(calendar): sliced multi-day events start at 00:00, not 23:59

[ago1776]

Fixes #4206.

Problem

With sliceMultiDayEvents: true, multi-day events are split into (1/n), (2/n), … Every slice after the first was rendered with a start time of 23:59 instead of the next day's 00:00.

Cause

In defaultmodules/calendar/calendar.js, the slicing loop reuses midnight (which is .endOf("day") = 23:59:59.999) as the start of the following slice:

event.startDate = midnight.format("x"); // 23:59:59.999 of the next day

Fix

Set the next slice's start to the beginning of that day:

event.startDate = midnight.clone().startOf("day").format("x");

Regression test

As requested, added an electron regression test (sliceMultiDayEvents slice start time) plus a scenario slice_multiday_timed_start_midnight and a fixture with a timed event spanning several midnights (Fri 12:00 → Mon 08:00). It asserts that every rendered slice time cell contains a 00:00 start and never 23:59.

Verified locally:

• with the fix: test passes;
• without the fix: test fails on 23:59.

prettier, eslint and cspell are clean on the changed files.

[KristjanESPERANTO]

@ago1776 Thanks for that. But please point your PR to the devlop branch, not to master.

[ago1776]

Retargeted this PR from master to develop and rebased the branch accordingly, per the contribution guidelines. The diff is unchanged — the one-line fix plus the regression test/mock/config. Thanks for the review!

[KristjanESPERANTO]

LGTM! Thanks :)