---
name: "dysize"
section: "3"
platform: "linux"
package: "man-pages"
version: "6.19-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/dysize"
---

# dysize(3)

get number of days for a given year

## NAME

dysize - get number of days for a given year

## LIBRARY

Standard C library (*libc*, *-lc*)

## SYNOPSIS

```
#include <time.h>
```

**int dysize(int** *year***);**

Feature Test Macro Requirements for glibc (see [**feature\_test\_macros**(7)](/feature_test_macros/7.md)):

**dysize**():

```
    Since glibc 2.19:
        _DEFAULT_SOURCE
    glibc 2.19 and earlier:
        _BSD_SOURCE || _SVID_SOURCE
```

## DESCRIPTION

The function returns 365 for a normal year and 366 for a leap year. The calculation for leap year is based on:

```
(year) %4 == 0 && ((year) %100 != 0 || (year) %400 == 0)
```

The formula is defined in the macro *\_\_isleap(year)* also found in *\<time.h\>*.

## ATTRIBUTES

For an explanation of the terms used in this section, see [**attributes**(7)](/attributes/7.md).

| | | |
| --- | --- | --- |
| **Interface** | **Attribute** | **Value** |
| **dysize**() | Thread safety | MT-Safe |

## STANDARDS

None.

## HISTORY

SunOS 4.x.

This is a compatibility function only. Don't use it in new programs.

## SEE ALSO

[**strftime**(3)](/strftime/3.md)