# Use Case: Changes and Freeze Windows of Every Business Unit

Source: [https://docs.virtosoftware.com/docs/calendar-overlay-pro/working-with-virto-calendar/use-case-change-and-freeze-calendar/](https://docs.virtosoftware.com/docs/calendar-overlay-pro/working-with-virto-calendar/use-case-change-and-freeze-calendar/)
Product: Virto Calendar App
Updated: 2026-10-23


This use case shows how IT sees every business unit's changes, releases and freeze windows in one calendar, coloured by unit, without a consolidated change list to maintain. A change scheduled into another unit's freeze, or three releases on the same night, becomes visible while one of them can still move.

[Open the interactive demo](https://app.storylane.io/demo/zvsgjkoywzzf)

**Interactive demo walkthrough**
1. Changes and freezes in one view — Every business unit's changes, releases and freeze windows on one calendar, coloured by unit.
2. Q4 for every business unit: changes, releases and freezes, coloured by unit. Two year-end freezes from different units start on 15 December.
3. The week of 13 December: Logistics' peak freeze runs all week, two year-end freezes start on Tuesday, and on Friday evening an emergency change lands inside all three.
4. The change's card reads its list item: Logistics, high risk, approved by the CAB. Whether it may run inside the freeze is a decision the calendar puts in front of you.
5. August in Month view: releases and changes across sites, with times. The emergency VPN change in Madrid runs from Wednesday evening into Thursday.
6. Filter by business unit to see one unit's quarter. Here only Logistics is left: a database change, three releases, its peak freeze and an emergency change.
7. Here the changes come from one SharePoint list with a Business Unit column. Other units' change and maintenance lists are added as further sources.
8. Put every unit's changes on one calendar — Virto Calendar App runs in your Microsoft 365 tenant; the change records stay in the lists your sites already keep.

## What you need

- **Virto Calendar App** in your Microsoft 365 tenant.
- The SharePoint lists in which the units keep their changes, releases and maintenance or freeze windows. Each needs a title, a start and an end column. Freeze windows are ordinary items that span several days.

The changes can be kept in two ways, and the calendar handles both:

- **One list per unit**, for example a data center, a plant or a retail region. Each list becomes a data source with its own colour.
- **One shared list with a Business Unit column**, as in the demo. The list is one data source, coloured by that column.

## Step 1. Add the change lists

1. Open the calendar settings by clicking the calendar name.
2. Add each change, release and maintenance list as a SharePoint data source, mapping its own start and end columns. See [Adding a New Data Source](https://docs.virtosoftware.com/docs/calendar-overlay-pro/data-sources/sharepoint-list-as-a-data-source/adding-a-new-data-source/index.md).
3. Tick **Read only** where the calendar should only show the records: they stay in the list that owns them, and readers see them through the permissions they already have.

## Step 2. Colour by unit

- With one list per unit, give each data source its own colour.
- With one shared list, edit the data source, open the **Color code** tab, select the **Business Unit** column and give each unit a colour.

If several lists use the same category names, [Unify Categories](https://docs.virtosoftware.com/docs/calendar-overlay-pro/settings/unify-categories/index.md) gives matching categories one colour across sources.

## Step 3. Read the collisions

- **Week** shows freeze and maintenance windows as all-day bars along the top, so a change inside them is read against them. An emergency change still happens during a freeze; here the CAB sees which window it entered and whose.
- **Month** shows releases from different sites landing on the same night. A change that starts in the evening and runs past midnight is drawn across both days.
- **Year Quarter** shows which unit owns the density of a quarter.

The lists, colours and permissions stay the same at every scale. See [Simple Views](https://docs.virtosoftware.com/docs/calendar-overlay-pro/calendar-views/simple-views/index.md).

## Step 4. Open the record

Click a change to open its card with the columns of its list item, such as the unit, the risk and the CAB approval. Choose which columns the card shows in the data source's tooltip settings.

## What the app does not do

Virto Calendar App shows when a change happens. Change records, risk assessment, approvals and the CAB workflow stay in the IT service management tool or the SharePoint list that owns them.