---
title: 5.5 localtime()
description: "## Overview The `localtime()` function converts a calendar time stored as a `time_t` value into a **broken-down local date and time**. Instead of returning a formatted string like `ctime()`, `localtime()` returns a pointer to a `struct tm` containing individual date…"
url: "https://edcret.in/docs/linux-os/system-calls/time-system-calls/c-localtime-function/"
updated: "2026-07-27"
category: Linux OS / System Calls / Time System Calls
---

# 5.5 localtime()

## Overview

The `localtime()` function converts a calendar time stored as a `time_t` value into a **broken-down local date and time**.

Instead of returning a formatted string like `ctime()`, `localtime()` returns a pointer to a `struct tm` containing individual date and time components such as the year, month, day, hour, minute, and second.

## Header File

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

## Man Pages

```
man 3 localtime
```

## Function Prototype

```
struct tm *localtime(const time_t *timer);
```

## Parameters

| Parameter | Description |
| --- | --- |
| `timer` | Pointer to a `time_t` object containing the calendar time to be converted. |

## Return Value

On success, `localtime()` returns a pointer to a `struct tm` containing the local date and time.

On failure, it returns:

```
NULL
```

## Data Types

### `struct tm`

`struct tm` stores the individual components of a date and time.

```
struct tm
{
    int tm_sec;
    int tm_min;
    int tm_hour;
    int tm_mday;
    int tm_mon;
    int tm_year;
    int tm_wday;
    int tm_yday;
    int tm_isdst;
};
```

| Member | Description |
| --- | --- |
| `tm_sec` | Seconds (0–60) |
| `tm_min` | Minutes (0–59) |
| `tm_hour` | Hours (0–23) |
| `tm_mday` | Day of the month (1–31) |
| `tm_mon` | Month since January (0–11) |
| `tm_year` | Years since 1900 |
| `tm_wday` | Days since Sunday (0–6) |
| `tm_yday` | Days since January 1 (0–365) |
| `tm_isdst` | Daylight Saving Time flag |

## Examples

### Example 1 – Display Local Date and Time

#### main.c

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

int main(void)
{
    time_t current_time;
    struct tm *local;

    current_time = time(NULL);

    local = localtime(&current_time);

    printf("Date : %02d-%02d-%04dn",
           local->tm_mday,
           local->tm_mon + 1,
           local->tm_year + 1900);

    printf("Time : %02d:%02d:%02dn",
           local->tm_hour,
           local->tm_min,
           local->tm_sec);

    return 0;
}
```

#### Output

```
Date : 27-07-2026
Time : 15:45:32
```

> The output will be different on your system.

#### Explanation

```
current_time = time(NULL);
```

Obtains the current calendar time.

```
local = localtime(&current_time);
```

Converts the calendar time into a `struct tm` representing the local date and time.

```
local->tm_mon + 1
```

`tm_mon` stores months in the range **0–11**, where January is `0`. Adding `1` converts it to the familiar range **1–12**.

```
local->tm_year + 1900
```

`tm_year` stores the number of years since **1900**. Adding `1900` gives the current year.

---

### Example 2 – Display Individual Date and Time Components

#### main.c

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

int main(void)
{
    time_t current_time;
    struct tm *local;

    current_time = time(NULL);
    local = localtime(&current_time);

    printf("Hour   : %dn", local->tm_hour);
    printf("Minute : %dn", local->tm_min);
    printf("Second : %dn", local->tm_sec);

    return 0;
}
```

#### Output

```
Hour   : 15
Minute : 45
Second : 32
```

> The output will be different on your system.

#### Explanation

Each member of the `struct tm` can be accessed using the `->` operator because `localtime()` returns a pointer to the structure.

## Notes

- `localtime()` converts a `time_t` value into **local date and time**.
- It returns a pointer to a `struct tm`.
- `tm_mon` ranges from **0** to **11**, so add `1` when displaying the month.
- `tm_year` represents the number of years since **1900**, so add `1900` to obtain the actual year.
- The returned pointer refers to **statically allocated memory** managed by the C library.
- Each call to `localtime()` may overwrite the result of a previous call.
- Do not modify or free the returned structure.

## Related Functions

- `time()`
- `ctime()`
- `gmtime()`
- `mktime()`
- `strftime()`