> For the complete documentation index, see [llms.txt](https://threadforge.gitbook.io/threadlink-documentation/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://threadforge.gitbook.io/threadlink-documentation/engineer-reference/chronos.md).

# Chronos: Time

Chronos's time members are static; `Start()` and `Stop()` are instance methods.

| Member                                                                                | Semantics                                                                                                                      |
| ------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------ |
| `TimeScale`                                                                           | Accepts only 0 or 1; other values, and the current value, are ignored. Setting it publishes `OnGamePaused` or `OnGameResumed`. |
| `RawTimeScale`                                                                        | Same restriction; publishes nothing.                                                                                           |
| `DeltaTime`, `SmoothDeltaTime`, `UnscaledDeltaTime`                                   | Cached once per `OnUpdate`.                                                                                                    |
| `FixedDeltaTime`                                                                      | Cached once per `OnFixedUpdate`.                                                                                               |
| `CurrentFramerate`                                                                    | `1 / DeltaTime`.                                                                                                               |
| `CurrentTimeSinceDeployment`                                                          | Unity's `Time.time`, cached each `OnUpdate`.                                                                                   |
| `TotalPlaytime`, `CountTotalPlaytime`, `PlaytimeCountingMode`, `ClearTotalPlaytime()` | `PlaytimeCountMode` is `Scaled` (the default) or `Unscaled`.                                                                   |
| `Start()`, `Stop()`                                                                   | Subscribe and unsubscribe the tick handlers.                                                                                   |

`Boot()` resets `TotalPlaytime` to zero, turns on `CountTotalPlaytime` and starts the tick handlers. While `CountTotalPlaytime` is on, each frame publishes `OnPlaytimeCountTick` with the running total.

Chronos updates its values from the Iris update events. In `Custom` update-loop mode, they are only as current as the project's own `OnUpdate` and `OnFixedUpdate` publications.

## Manual physics simulation

With `ChronosConfig.IrisPhysicsUpdate` on, `Chronos.Boot()` sets `Physics.simulationMode = SimulationMode.Script` and calls `Physics.Simulate(Time.fixedDeltaTime)` on each `OnFixedUpdate`.

Leave it off if another framework owns the simulation. The simulation mode is global: if other code also steps physics in script mode, physics steps twice. Nothing guards against this.