calendar_copy_offset_holidays_in_week.yaml

blueprint:
  name: Create Calendar Events with Offset Holidays in Week
  description: Copy Events (in the next 365 days) from one local calendar to another.  Look
    in the holidays calendar and shift events for each public holiday  in the week
    before the event.
  domain: script
  source_url: https://gist.github.com/bruxy70/b55acd9d69de4b8d8880f63e6dcb44cd
  input: {}
fields:
  source_calendar:
    name: Source calendar
    description: Calendar with the events to be copied from
    required: true
    selector:
      entity:
        filter:
          integration: local_calendar
  destination_calendar:
    name: Destination calendar
    description: Calendar for the events to be copied to
    required: true
    selector:
      entity:
        filter:
          integration: local_calendar
  public_holidays:
    name: Public Holidays
    description: Calendar with the public holidays to be avoided
    required: true
    selector:
      entity:
        filter:
          integration: holidays
sequence:
- service: calendar.get_events
  data:
    duration:
      days: 365
  target:
    entity_id: '{{ source_calendar }}'
  response_variable: source
- service: calendar.get_events
  data:
    duration:
      days: 365
  target:
    entity_id: '{{ destination_calendar }}'
  response_variable: destination
- service: calendar.get_events
  data:
    duration:
      days: 365
  target:
    entity_id: '{{ public_holidays }}'
  response_variable: holidays
- variables:
    holiday_dates: |-
      {%- set ns = namespace(dates={}) %}
      {%- if holidays[public_holidays]["events"] %}
        {%- for event in holidays[public_holidays]["events"] %}
          {%- set ns.dates = dict(ns.dates, **{event.start:event.summary}) %}
        {%- endfor %}
      {%- endif %}
      {{ ns.dates}}
    destination_dates: |-
      {%- set ns = namespace(dates={}) %}
      {%- if destination[destination_calendar]["events"]%}
        {%- for event in destination[destination_calendar]["events"] %}
          {%- set ns.dates = dict(ns.dates, **{event.start:event.summary}) %}
        {%- endfor %}
      {%- endif %}
      {{ ns.dates}}
- repeat:
    for_each: '{{ source[source_calendar]["events"] }}'
    sequence:
        - variables:
            offset: >-
              {%- set ns = namespace(offset=0,in_week=False,found=False) %}
              {%- set collection_date = strptime(repeat.item.start,"%Y-%m-%d").date() %}
              {%- for i in range(collection_date.weekday()+1) %}
                {%- set d = ( collection_date + timedelta( days=-i) ).isoformat() %}
                {%- if d in holiday_dates %}
                  {%- set ns.in_week = true %}
                  {%- set ns.offset = ns.offset + 1 %}
                {%- endif %}
              {%- endfor %}
              {%- if ns.in_week %}
                {# Increase offset until we find a date that is not public holiday #}
                {%- for _ in range(7) if not ns.found %}
                  {%- set start = strptime(repeat.item.start,"%Y-%m-%d").date() %}
                  {%- set d = ( start + timedelta( days=ns.offset) ).isoformat() %}
                  {%- if d in holiday_dates %}
                    {%- set ns.offset = ns.offset + 1 %}
                  {% else %}
                    {%- set ns.found = true %}
                  {%- endif %}
                {% endfor %}               
              {%- endif %} 
              {{ ns.offset }}
            start_date: >-
              {%- set start = strptime(repeat.item.start,"%Y-%m-%d").date() %}
              {{ (start + timedelta(days=offset)).isoformat() }}
            end_date: >-
              {%- set end = strptime(repeat.item.end,"%Y-%m-%d").date() %}
              {{ (end + timedelta(days=offset)).isoformat() }}
            summary: "{{ repeat.item.summary }}"
        - if:
            - condition: template
              value_template: "{{ start_date not in destination_dates }}"
          then:
            - service: calendar.create_event
              data:
                summary: "{{ summary }}"
                start_date: "{{ start_date }}"
                end_date: " {{ end_date }}"
              target:
                entity_id: "{{ destination_calendar }}"
mode: single
icon: mdi:calendar-blank-multiple

Thanks for this contribution, I have updated the blueprint to this.