# Time Segment Setup ## Creating/Editing Time Segments Time Segments are managed in the Time Segments step of the **Variable** dialog.

Screenshot of the Time Segments step of the Variables wizard — Time Segment step of the Variable dialog

You can add, edit and duplicate Time Segments just like any other item in a [**list view**](/using-taglo-software/the-taglo-interface/list-views.md). ## The Time Segment Wizard ### Timings You must define the time period over which each Time Segment applies. This time period is defined in terms of three settings: 1. **From**: The period at which the segment starts 2. **Duration**: The length of the segment 3. **To**: The period at which the segment ends As shown in the screenshot below, these settings can be quickly edited by clicking on the relevant editing shortcut button

Screenshot showing two Time Segments with timings editing shortcut buttons highlighted — Timings editing shortcuts

**From** and **To** settings can be set to one of the following:

From/To setting	Details
`Auto`	Period dependent on context: If first segment, From will be set to the start of the model If last segment, To will be set to the end of the model If other, From/To will be based on end or beginning of adjacent segments).
`Fixed Period`	Choice of specific periods from the Model timings (e.g. Q2 2030)
`Periods from Start`	Number of periods from start (first period = 1 )
`Periods from End`	Number of periods from end (last period = 1)

**Duration** can be set to one of the following:

Duration setting	Details
`Fill`	Segment will stretch to end of previous period and beginning of next (or to start/end of the model if first/last segment)
`Number of periods`	Segment will occupy the specified number of periods

{% hint style="warning" %} You should apply a **maximum of 2** of the three settings. Which settings are applied depends on the Time Segment. For instance, the first Time Segment never needs to have the **From** setting applied, as it always starts at the first period. If you set **From** to a period that is not the first period, a warning will be shown. Likewise, if you set both the **Duration** and the **To** settings of the first Time Segment, one of these will be redundant, and they may clash. {% endhint %} ### Formula The **Formula** of a Time Segment determines how that Time Segment calculates its values. There are five possible formula types for each Time Segment:

Formula Type	Details
`Auto`	Applies the default Calculation of the Variable. (This option is not available for an Assumptions Type Variable).
`Assumptions`	Links to specific Assumptions. See Creating/Referencing Assumptions for more details.
`Calculation`	Applies a custom Calculation that cannot refer to other Variables. (See more details below).
`Aggregation`	Used for an Aggregation Variable. Cannot be manually selected - applied automatically when using Aggregation.
`Rearranged`	Used when Rearranging. Cannot be manually selected - applied automatically when Rearranging

#### Calculation Formula

As shown in the above example, a Time Segment with a Calculation formula acts similarly to an Assumptions Time Segment. In this example, `Price inflation` is a Variable of type `Assumptions`. In the first period, an Assumptions Time Segment links to an input. We then use a Calculation Time Segment for the remaining periods to reference the previous period, rather than linking to specific Assumptions for each period of the Model. {% hint style="info" %} `Calculation` Time Segments act similarly to `Assumptions`, in that they specify an **input** to the Model. For this reason, calculations in Time Segments cannot reference other Variables. If you want to perform a calculation referencing other Variables, the Variable itself must be of type `Calculation.` If you are not sure when to use Assumption/Calculation Variables and Assumption/Calculation Time Segments, you may want to read about the [**Rearranging feature**](/rearranging/rearranging-example.md), which helps deal with complex scenarios. {% endhint %} ## Time Segment shortcuts

Screenshot showing the Time Segments step of the Variable wizard, highlighting the shortcut buttons used for editing Time Segments — Time Segment shortcuts

Several shortcuts are provided in the Time Segment interface to speed up some common operations, as shown in the image above.

Shortcut	Details
1) Insert period	Inserts a period of duration 1 period at the start of the Model
2) Make all equal to first period	Inserts a single period segment of type `Assumptions` at the start of the Model, and a second segment with a `Calculation` of `Variable [-1]` for the rest of the Model timings (as per the example shown in the image above).
3) Change formula type	Opens a dropdown to quickly switch between formula types.
4) Reset to default segment type	For a Calculation Variable, resets Time Segment to `Auto`. For an Assumptions Variable, resets Time Segment to `Assumptions`.

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