---
title: TimeInterval
framework: foundation
role: symbol
role_heading: Type Alias
path: foundation/timeinterval
---

# TimeInterval

A number of seconds.

## Declaration

```swift
typealias TimeInterval = Double
```

## Discussion

Discussion A TimeInterval value is always specified in seconds; it yields sub-millisecond precision over a range of 10,000 years. On its own, a time interval does not specify a unique point in time, or even a span between specific times. Combining a time interval with one or more known reference points yields a Date or DateInterval value.

## See Also

### Date Representations

- [Date](foundation/date.md)
- [DateInterval](foundation/dateinterval.md)