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# PostgreSQL JUSTIFY_DAYS() Function

**Summary**: in this tutorial, you will learn how to use the PostgreSQL `JUSTIFY_DAYS()` function to adjust 30-day intervals as months.

## Introduction to the PostgreSQL JUSTIFY_DAYS() function

The `JUSTIFY_DAYS()` function allows you to normalize an [interval](../postgresql-tutorial/postgresql-interval) by converting days exceeding 30 days into months and remaining days.

Here's the basic syntax of the `JUSTIFY_DAYS()` function:

```sql
JUSTIFY_DAYS ( value) → interval
```

In this syntax:

- `value` is an interval value you want to justify.

The `JUSTIFY_DAYS()` function returns an adjusted interval with:

- Days exceeding 30 converted to months.
- The remaining days are kept as days.
- Hours, minutes, and seconds remain intact.

If the input interval (`value`) is `NULL`, the function returns `NULL`.

## PostgreSQL JUSTIFY_DAYS() function examples

Let's explore some examples of using the PostgreSQL `JUSTIFY_DAYS()` function.

### 1) Basic PostgreSQL JUSTIFY_DAYS() function example

The following statement uses the `JUSTIFY_DAYS()` function to adjust intervals that are multiples of 30 days:

```sql
SELECT JUSTIFY_DAYS(INTERVAL '30 days'),
       JUSTIFY_DAYS(INTERVAL '60 days'),
       JUSTIFY_DAYS(INTERVAL '90 days');
```

Output:

```text
 justify_days | justify_days | justify_days
--------------+--------------+--------------
 1 mon        | 2 mons       | 3 mons
(1 row)
```

### 2) Using JUSTIFY_DAYS() function with intervals that are not multiple of 30 days

The following example uses the `JUSTIFY_DAYS()` function to adjust intervals that are not multiples of 30 days:

```sql
SELECT JUSTIFY_DAYS(INTERVAL '15 days'),
       JUSTIFY_DAYS(INTERVAL '45 days'),
       JUSTIFY_DAYS(INTERVAL '75 days');
```

Output:

```text
 justify_days | justify_days  |  justify_days
--------------+---------------+----------------
 15 days      | 1 mon 15 days | 2 mons 15 days
(1 row)
```

### 3) Using JUSTIFY_DAYS() function with intervals that include hours

The following example uses the `JUSTIFY_DAYS()` function to adjust intervals that include hours, minutes, and seconds:

```sql
SELECT JUSTIFY_DAYS(INTERVAL '15 days 2 hours'),
       JUSTIFY_DAYS(INTERVAL '55 days 30 minutes'),
       JUSTIFY_DAYS(INTERVAL '75 days 45 seconds');
```

Output:

```text
   justify_days   |      justify_days      |      justify_days
------------------+------------------------+-------------------------
 15 days 02:00:00 | 1 mon 25 days 00:30:00 | 2 mons 15 days 00:00:45
(1 row)
```

The output indicates that the adjusted intervals have the time parts.

## Summary

- Use the `JUSTIFY_DAYS()` function to normalize an interval by converting days exceeding 30 days as months.

---

## Related docs (Date Functions)

- [AGE](https://neon.com/postgresql/postgresql-date-functions/postgresql-age)
- [AT TIME ZONE Operator](https://neon.com/postgresql/postgresql-date-functions/postgresql-at-time-zone)
- [CLOCK_TIMESTAMP](https://neon.com/postgresql/postgresql-date-functions/postgresql-clock_timestamp)
- [CURRENT_DATE](https://neon.com/postgresql/postgresql-date-functions/postgresql-current_date)
- [CURRENT_TIME](https://neon.com/postgresql/postgresql-date-functions/postgresql-current_time)
- [CURRENT_TIMESTAMP](https://neon.com/postgresql/postgresql-date-functions/postgresql-current_timestamp)
- [DATE_PART](https://neon.com/postgresql/postgresql-date-functions/postgresql-date_part)
- [DATE_TRUNC](https://neon.com/postgresql/postgresql-date-functions/postgresql-date_trunc)
- [EXTRACT](https://neon.com/postgresql/postgresql-date-functions/postgresql-extract)
- [ISFINITE](https://neon.com/postgresql/postgresql-date-functions/postgresql-isfinite)
- [JUSTIFY_HOURS](https://neon.com/postgresql/postgresql-date-functions/postgresql-justify_hours)
- [JUSTIFY_INTERVAL](https://neon.com/postgresql/postgresql-date-functions/postgresql-justify_interval)
- [LOCALTIME](https://neon.com/postgresql/postgresql-date-functions/postgresql-localtime)
- [LOCALTIMESTAMP](https://neon.com/postgresql/postgresql-date-functions/postgresql-localtimestamp)
- [MAKE_DATE](https://neon.com/postgresql/postgresql-date-functions/postgresql-make_date)
- [MAKE_INTERVAL](https://neon.com/postgresql/postgresql-date-functions/postgresql-make_interval)
- [MAKE_TIME](https://neon.com/postgresql/postgresql-date-functions/postgresql-make_time)
- [NOW](https://neon.com/postgresql/postgresql-date-functions/postgresql-now)
- [PG_SLEEP](https://neon.com/postgresql/postgresql-date-functions/postgresql-pg_sleep)
- [STATEMENT_TIMESTAMP](https://neon.com/postgresql/postgresql-date-functions/postgresql-statement_timestamp)
- [TIMEOFDAY](https://neon.com/postgresql/postgresql-date-functions/postgresql-timeofday)
- [TO_DATE](https://neon.com/postgresql/postgresql-date-functions/postgresql-to_date)
- [TO_TIMESTAMP](https://neon.com/postgresql/postgresql-date-functions/postgresql-to_timestamp)