---
title: systemClockDidChange
framework: foundation
role: symbol
role_heading: Type Property
path: foundation/notificationcenter/messageidentifier/systemclockdidchange
---

# systemClockDidChange

An identifier for a message about a change in the system clock.

## Declaration

```swift
static var systemClockDidChange: NotificationCenter.BaseMessageIdentifier<Date.SystemClockDidChangeMessage> { get }
```

## Discussion

Discussion Use this identifier with NotificationCenter’s addObserver(of:for:using:) or messages(of:for:bufferSize:) methods to observe messages of type Date.SystemClockDidChangeMessage.

## See Also

### Identifying calendar, date, and time zone messages

- [calendarDayChanged](foundation/notificationcenter/messageidentifier/calendardaychanged.md)
- [systemTimeZoneDidChange](foundation/notificationcenter/messageidentifier/systemtimezonedidchange.md)