Hour slots are calculated with DST, causing duplicate hour to appear in single day view

[ptcs-juma]

How to reproduce the bug:

1. Use Finnish time zone

• Europe/Helsinki
• Eastern Europe Standard Time
• FLE Standard Time

2. Setup data so that only one day is "selected".

• Day: 2024-03-31
• Start hour: 2
• End hour: 5

3. Draw the calendar
4. The calendar should now include duplicate times for 04:00+03:00 hour.

This is caused by changes made in PR #46. The original method was correct as the time was adjusted based on UTC-time, but after the changes, the time is tied on the user's time zone rules.

Setting the hour to 3 or 4 for the original 2024-03-01 00:00:00+02:00 time produces 2024-03-01 04:00:00+03:00 time, thus a duplicate hour slot.

Using the original way of calculating hours generates correct times as seen below.

  private createDate(date: Date, hours: number, minutes: number): Date {
    const newDate = new Date(date);
    // Move UTC-time forwards.
    newDate.setTime(newDate.getTime() + (hours * 3600000) + (minutes * 60000));
    return newDate;
  }