---
type: "fhirpath-function"
title: "FHIRPath Function: dayOf"
function: "dayOf"
category: "Utility functions"
section: "5.10.8.3"
source: "fhirpath/functions.json"
---
# FHIRPath Function: dayOf
_No canonical section match found in index.md._
## Summary
- **Category**: Utility functions
- **Section**: `5.10.8.3`
- **Return Type**: `Integer`
- **Empty Input Result**: `empty`
- **Errors on Multiple Input**: `true`
## Description
If the input collection contains a single Date or DateTime, this function will return the day component.
## Arguments
- none
## Type Mapping
- `Date-Integer`
- `DateTime-Integer`
## Example
```fhirpath
@2014-01-05T10:30:00.000.dayOf() // 5
```