Putting a Twin on a Calendar

Give a twin a time unit and a start date, and its timesteps become real dates: weeks, months, quarters. Read results per month or year, follow today's date, and let viewers pick a time range — without changing a single computed value.

By default a twin counts its timesteps: 1, 2, 3 … That is enough for many simulations, but once your twin stands for real business, you'll want to read its results as dates: "week of 19 Jan", "Q3 2026", "this month so far". Giving a twin a calendar does exactly that. It changes how timesteps are labelled and grouped, never the numbers your simulation computes.

Set up the calendar

In the Model Navigator, select the twin. In the Properties panel, find the Timescale section.
Choose a Time unit: what one unit of scenario time means for this twin (Day, Week, Month, Quarter, Year …). Pick the coarsest period you think in. A planning twin that works in months and years usually takes Year.
Enter the date of the First step: the calendar date of your scenario's first timestep. Until you set it, the panel says No calendar date set — timesteps are counted, not dated.
Select each scenario and choose its Step, e.g. 1 week, 1 month, 1 quarter. The step must fit evenly into the twin's time unit. dt is then filled in for you (Derived from the step): a monthly step in a year twin gives dt = 1/12.

The twin's panel lists every scenario with the period it covers, e.g. 5 Jan 2026 – 15 Jun 2026. If something doesn't fit together, for example a scenario without a step or a start that falls between two periods, the panel tells you what to change.

What you get

Dates instead of step numbers in time-series grids, chart axes and the round control.
Show per: a chart or value tile can show a weekly or daily series per month, quarter or year. Combine as decides how the steps of one period become one value: Sum for flows (orders, revenue), Last value for stocks (inventory, cash), or Average, Minimum or Maximum. A period that isn't finished yet is marked as partial (so far) rather than shown as complete.
Value tiles that follow today: under Reads, choose Now (live) or Previous period (live) and the tile always shows the current period.
Dashboard time ranges: in the dashboard's properties, set a Default time range: Whole scenario, This year, Last year, Year to date, Last 12 months or Custom. Add a Time range chooser from the Toolbox to let viewers switch it themselves. Switching doesn't change the model. On a Live data scenario, picking a range also fetches its missing periods (see Bringing Live Data into a Twin).

Changing the calendar later

You can change the time unit or the first-step date at any time. Metapad then asks Re-date stored values?: your values keep their numbers but refer to different dates. Nothing is recalculated, so moving the start of a plan by a month is a safe, one-step change, and you can undo it.

Example: the Beer Game

The Beer Game template runs on a weekly calendar. Its 24 rounds are the weeks from 5 January to 15 June 2026. Open the twin's Timescale section to see the setting, and try a chart with Show per: Month to see the weekly orders summed by month.

Next steps

Creating Twins and Scenarios — where twins, scenarios and their timelines come from
Adding Charts, Sliders, and Checkboxes — the widgets that show per month or per year
Playing Through a Simulation Step by Step — the round control shows each round's date
Bringing Live Data into a Twin — fill a calendar twin with actual figures