Date Functions

Dates and times are everywhere in data—logins, transactions, signups, events, deadlines, and more. Being able to work with that kind of time-based information is essential in almost every application and analysis. That’s where PostgreSQL’s date functions come in.

In this overview, we’ll introduce what PostgreSQL date functions are, why they’re useful, and how they’re commonly used in real-world scenarios.

What Are Date Functions in PostgreSQL?

Date functions in PostgreSQL are built-in tools that allow you to manipulate, format, and extract information from date and time values. These functions help you answer questions like:

• What day of the week was this date?

• How many days are left until an event?

• What’s the difference between two timestamps?

• Can I round a timestamp to the beginning of the month?

PostgreSQL has strong support for various date and time types—such as DATE, TIME, TIMESTAMP, and TIMESTAMPTZ (timestamp with time zone)—as well as a wide set of functions and operators to work with them.

Why Are Date Functions Useful?

Working with dates is more than just displaying a calendar value. It’s about gaining insight and control over how your data behaves over time.

Date functions allow you to:

• Group and filter data by time periods (day, week, month, etc.)

• Calculate time differences and durations

• Format dates for reports and exports

• Handle time zones and global events accurately

• Automate recurring schedules, reminders, or monitoring

They also make it easier to write queries that are more expressive, accurate, and dynamic when handling time-related data.

Real-World Use Cases

Date functions are used across many industries and systems. For example:

• In e-commerce, to calculate customer lifetime or time since last purchase

• In finance, to group revenue by quarter or forecast future cash flows

• In healthcare, to check if a prescription is overdue or how long since a visit

• In SaaS platforms, to generate activity reports or identify churn risk based on inactivity

• In project management, to calculate days remaining or time spent on tasks

Any application that logs events, schedules tasks, or reports on historical data can benefit from PostgreSQL’s time-handling capabilities.

What Will You Learn in This Section?

This section of the documentation introduces the essential date and time tools PostgreSQL provides. Topics include:

• Understanding the core data types: DATE, TIME, TIMESTAMP, TIMESTAMPTZ

• Using system values like CURRENT_DATE and CURRENT_TIMESTAMP

• Extracting date parts with EXTRACT

• Truncating dates with DATE_TRUNC

• Adding and subtracting dates and times

• Working with intervals

• Formatting with TO_CHAR

• Handling time zone conversions

Each topic will include practical examples, so you can immediately see how these functions apply to real scenarios.