---
title: tolerance
framework: foundation
role: symbol
role_heading: Instance Property
path: foundation/nsbackgroundactivityscheduler/tolerance
---

# tolerance

A value of type TimeInterval, which specifies a range of time during which the background activity may occur.

## Declaration

```swift
var tolerance: TimeInterval { get set }
```

## Discussion

Discussion A nominal fire date for scheduled background activity is calculated based on a combination of the interval property value and the time the activity began or the last execution date. The tolerance property specifies a grace period—a range of time before and after the nominal fire date, during which the activity may be invoked. As the activity nears the end of its grace period, the system schedules the activity more aggressively. The default tolerance period is half the value of the interval property. See Configure Scheduler Properties.

## See Also

### Related Documentation

- [TimeInterval](foundation/timeinterval.md)

### Background Scheduler Attributes

- [identifier](foundation/nsbackgroundactivityscheduler/identifier.md)
- [repeats](foundation/nsbackgroundactivityscheduler/repeats.md)
- [interval](foundation/nsbackgroundactivityscheduler/interval.md)
- [qualityOfService](foundation/nsbackgroundactivityscheduler/qualityofservice.md)
- [shouldDefer](foundation/nsbackgroundactivityscheduler/shoulddefer.md)