---
title: TimeZone.SystemTimeZoneDidChangeMessage
framework: foundation
role: symbol
role_heading: Structure
path: foundation/timezone/systemtimezonedidchangemessage
---

# TimeZone.SystemTimeZoneDidChangeMessage

A message the system sends when the system time zone changes.

## Declaration

```swift
struct SystemTimeZoneDidChangeMessage
```

## Overview

Overview Observe this message with the identifier systemTimeZoneDidChange, or specify its type directly to the addObserver(of:for:using:) method. The Subject of this message type is TimeZone. This message interoperates with the notification NSSystemTimeZoneDidChange. 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 time zone change

- [init(previousTimeZone:)](foundation/timezone/systemtimezonedidchangemessage/init(previoustimezone:).md)

### Accessing message properties

- [previousTimeZone](foundation/timezone/systemtimezonedidchangemessage/previoustimezone.md)

## Relationships

### Conforms To

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