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Date Formatter

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Format any date into DD/MM/YYYY, ISO 8601, US style, long form, Unix timestamp, and more. Instant, in-browser date conversion with locale support.

Reviewed by the thecalcu.com team · Last updated June 20, 2026

What is a Date?

A Date Formatter takes a date in any common format and instantly converts it into multiple output formats, DD/MM/YYYY, ISO 8601, US format (MM/DD/YYYY), a written long form, Unix timestamp, and day of the week. Dates appear in a confusing variety of formats across databases, APIs, documents, and applications; a formatter removes the ambiguity by showing the same date in all standard representations simultaneously.

The input is flexible: you can paste an ISO date like 2026-06-18, a DD/MM/YYYY date like 18/06/2026, a US-style 06/18/2026, a Unix timestamp in seconds or milliseconds, or almost any standard date string. The formatter detects the format automatically.

Date format conversion matters in practice. Moving data between a MySQL database (which stores dates as YYYY-MM-DD) and an Excel spreadsheet (which displays dates as DD/MM/YYYY in Indian settings, or MM/DD/YYYY in US settings) requires knowing the exact format at each step. Similarly, API responses often return Unix timestamps that need to be shown as human-readable dates in a UI.

The Locale option controls the language and ordering of the long form output and the day name. The DD/MM/YYYY, ISO, US format, and Unix timestamp outputs are locale-independent.

Why Use a Date Formatter?

Date format confusion is one of the most common sources of data entry errors and bugs. A date like 05/06/2026 is 5 June in India and the UK but 6 May in the US, the same string, two different meanings. Formatting all dates into ISO 8601 for storage and then converting to locale-appropriate display formats eliminates this ambiguity.

The formatter is also useful for quick sanity checks: given a Unix timestamp in a log file, what date and day does it correspond to? Given a long date like "18th June 2026", what is its ISO representation for a database query?

Who Should Use This Formatter?

Developers, converting between date formats when working with APIs, databases, and front-end display logic.

Data analysts, ensuring consistency when combining date columns from sources that use different conventions (US vs Indian vs ISO).

HR and operations teams, converting dates from contracts, letters, and forms into the format required by HR software or payroll systems.

Students and researchers, finding the day of the week for historical dates, or understanding how different date representations relate to each other.

For formatting numbers and currency, see the Number Formatter and Rupee Formatter.

What Does the Date Formatter Give You?

All outputs update as you type:

  • DD/MM/YYYY, day-first format used in India, UK, and most of the world
  • ISO 8601, YYYY-MM-DD, the international standard for data storage
  • MM/DD/YYYY, month-first US format
  • Long Form, written-out date in the chosen locale language (e.g. "18 June 2026")
  • Unix Timestamp, seconds since 1 January 1970 UTC
  • Day of Week, the name of the weekday

How to use this Date calculator

  1. Enter a date in the Date / Timestamp field, any common format is accepted (ISO, DD/MM/YYYY, Unix timestamp, etc.).
  2. Choose a Locale to control the language of the long form and day name outputs.
  3. All six output formats appear instantly below.
  4. Click the Copy icon next to any output to copy it to your clipboard.
  5. Use the ISO output for database storage, the DD/MM/YYYY for Indian documents, or the Unix timestamp for API calls.

Formula & Methodology

Parsing: The input string is tested against these patterns in order:
1. All-digit string of 9–13 characters → Unix timestamp (≤10 digits = seconds, 11–13 digits = milliseconds)
2. D/M/YYYY, D-M-YYYY, D.M.YYYY → DD/MM/YYYY (day-first, international)
3. Any other string → passed to new Date(string) (handles ISO 8601, US format, RFC 2822, and most other standard date strings)

Output generation:
- DD/MM/YYYY: ${pad(day)}/${pad(month)}/${year} using local date parts (no timezone shift)
- ISO 8601: ${year}-${pad(month)}-${pad(day)}
- US format: ${pad(month)}/${pad(day)}/${year}
- Long form: Intl.DateTimeFormat(locale, { year: 'numeric', month: 'long', day: 'numeric' })
- Day of week: Intl.DateTimeFormat(locale, { weekday: 'long' })
- Unix: Math.floor(Date.getTime() / 1000)

Frequently Asked Questions

The formatter accepts ISO 8601 (2026-06-18), DD/MM/YYYY (18/06/2026), MM/DD/YYYY (06/18/2026), Unix timestamps (in seconds or milliseconds), and most standard date strings. For ambiguous inputs like 05/06/2026, where it is unclear whether 05 is the day or the month, enter the date in ISO format (YYYY-MM-DD) to be explicit.
ISO 8601 is the international standard for date representation: YYYY-MM-DD. It is unambiguous (no confusion between day and month), sorts correctly as a string, and is the format expected by databases, APIs, and programming languages. It is the recommended format for storing dates in JSON, CSV, or database fields.
A Unix timestamp is the number of seconds that have elapsed since 1 January 1970 00:00:00 UTC (the Unix epoch). It is a timezone-independent integer used extensively in databases, logs, and APIs. The formatter converts any date to its Unix timestamp and also accepts a Unix timestamp as input.
The Locale option controls the Long Form output and the Day of Week. For Indian locale (en-IN), the long form might be '18 June 2026' and the day 'Thursday'. For French (fr-FR), the long form would be '18 juin 2026'. The DD/MM/YYYY, ISO, US format, and Unix timestamp outputs are locale-independent.
DD/MM/YYYY places the day first and is standard in India, the UK, Australia, and most of the world. MM/DD/YYYY places the month first and is used primarily in the United States. The same date, 06/07/2026, means 6 July 2026 in DD/MM format and 7 June 2026 in MM/DD format, making explicit formats like ISO 8601 safer for international use.
Yes, paste a Unix timestamp (e.g. 1750244280) into the Date field and the formatter will parse it and output all formats. It handles both second-precision (10-digit) and millisecond-precision (13-digit) Unix timestamps.
No. The date formatting runs entirely in your browser using JavaScript's built-in Date and Intl.DateTimeFormat APIs. Nothing is uploaded or stored.
The formatter returns 'Invalid date' for dates that don't exist in the Gregorian calendar. If you enter a date with a valid structure but an impossible value (month 13, day 32), the tool detects that the parsed date does not match the intended input and reports it as invalid.
Long form dates like '18 June 2026' or 'June 18, 2026' are used in formal documents, reports, letters, and legal filings where numeric-only dates can be ambiguous or feel too terse. The locale option controls the language and ordering of the long form.
Yes, enter any past date and the Day of Week output shows which day it fell on. This is useful for confirming dates in historical research, verifying contract dates, or satisfying curiosity about when a birthday or anniversary occurred.
Also known as
date format converterconvert date formatdate to iso 8601dd/mm/yyyy formatunix timestamp converter