---
title: Date.SystemClockDidChangeMessage
framework: foundation
role: symbol
role_heading: Structure
path: foundation/date/systemclockdidchangemessage
---

# Date.SystemClockDidChangeMessage

A message the system sends when the system clock changes.

## Declaration

```swift
struct SystemClockDidChangeMessage
```

## Overview

Overview Various events can initiate this message, such as a call to settimeofday(_:_:), or if the person using the device changes values in Settings. Observe this message with the identifier systemClockDidChange, or specify its type directly to the addObserver(of:for:using:) method. The Subject of this message type is Date. This message interoperates with the notification NSSystemClockDidChange. The system notifies observers of the message when the NotificationCenter posts the notification. Similarly, the system notifies observers of the notification when it posts the message.

## Topics

### Creating a message for a system clock change

- [init()](foundation/date/systemclockdidchangemessage/init().md)

## Relationships

### Conforms To

- [NotificationCenter.MainActorMessage](foundation/notificationcenter/mainactormessage.md)
- [Sendable](swift/sendable.md)
- [SendableMetatype](swift/sendablemetatype.md)