ISO 8601 Converter | Convert Dates to ISO Format Online
ISO 8601 Date Formatter
Convert dates to and from ISO 8601 international standard format.
ISO 8601 Format
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Convert time durations to/from ISO 8601 duration format (e.g., P1Y2M3DT4H5M6S)
ISO 8601 Duration
P0D
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ISO 8601 Format Reference
| Format | Example | Description |
|---|---|---|
| Date | 2024-01-15 | Calendar date (extended format) |
| Date (basic) | 20240115 | Calendar date (basic format) |
| Time | 14:30:00 | Local time |
| DateTime | 2024-01-15T14:30:00 | Combined date and time |
| UTC | 2024-01-15T14:30:00Z | Date/time in UTC (Zulu) |
| With Offset | 2024-01-15T14:30:00+05:30 | Date/time with timezone offset |
| Week | 2024-W03 | Week number |
| Week Day | 2024-W03-1 | Week with day (1=Monday) |
| Ordinal | 2024-015 | Year and day of year |
| Duration | P1Y2M3DT4H5M6S | 1 year, 2 months, 3 days, 4 hours, 5 minutes, 6 seconds |
How to Use This Tool
- Format a Date: Select a date and time using the pickers, then choose your desired format (full with timezone, date only, time only, week number, or ordinal date). Click "Format to ISO 8601" to generate the standardized string.
- Parse ISO String: Switch to the "Parse ISO String" tab and paste any ISO 8601 formatted date. The tool breaks it down into components and shows the equivalent local time representation.
- Create Durations: Use the "Duration" tab to build ISO 8601 duration strings (P1Y2M3DT4H5M6S format). Specify years, months, days, hours, minutes, and seconds for interval representations.
- Copy Results: Click the copy button next to any output to copy the formatted string. Use these in API requests, database fields, or configuration files requiring ISO 8601 compliance.
Technical Details
ISO 8601 is the international standard for date and time representation, published by the International Organization for Standardization (ISO). It is designed to provide clear, unambiguous formats that are universally understood, eliminating regional confusion and ensuring reliable data exchange in APIs, databases, and logs. The basic format is YYYY-MM-DDTHH:MM:SS.sssZ, where 'T' separates the date from the time, and 'Z' indicates UTC (Coordinated Universal Time). Timezone offsets use the ±HH:MM format (e.g., +05:30 for India, -08:00 for Pacific Time). Using our **ISO 8601 Converter** ensures your timestamps always include this critical timezone information to prevent errors in distributed systems.
The standard supports multiple unambiguous representations: **calendar dates** (e.g., 2024-03-15), **week dates** (e.g., 2024-W11-5 for the 5th day of the 11th week of 2024), and **ordinal dates** (e.g., 2024-075 for the 75th day of the year). Durations are expressed in the P[n]Y[n]M[n]DT[n]H[n]M[n]S format—for example, P1Y2M3DT4H means "1 year, 2 months, 3 days, 4 hours." Time intervals can be expressed as a start/end pair, a start and a duration, or a duration and an end.
A key technical advantage of the YYYY-MM-DD format is that **ISO 8601 dates sort lexicographically**, meaning simple alphabetical string sorting produces perfect chronological order. This is a critical feature for efficient database indexing, organized log file analysis, and correctly sorted API responses. Use the tool on this page to generate dates that are guaranteed to sort correctly.
Common Mistakes to Avoid
- Omitting the Timezone Indicator: Using a format like "2024-03-15T10:00:00" without a
Z(for UTC) or offset like+05:00is a major source of bugs. This timestamp is ambiguous—different systems may interpret it as local time or UTC, leading to data inconsistencies in APIs, logs, and distributed systems. Our converter ensures your output always includes clear timezone information. - Using Slashes, Dots, or Incorrect Separators: Formats like "2024/03/15" or "2024.03.15" are not ISO 8601 compliant. The standard strictly requires hyphens for dates (
YYYY-MM-DD) and colons for time (HH:MM:SS). While some parsers are lenient, using non-standard separators will fail in strict validation environments. Our tool guarantees correct, standard-compliant formatting. - Misusing or Misunderstanding the Week Date Format: Week dates (e.g.,
2024-W01-1) follow specific ISO week numbering rules where Week 1 contains the year's first Thursday. This means December 31st can belong to Week 1 of the *next* year, causing significant errors if used for general calendar dates. Use this format only for explicit week-based reporting, not for everyday dates. - Mixing Basic and Extended Formats Incorrectly: The basic format (e.g.,
20240315) omits separators for compactness, while the extended format (2024-03-15) uses them for readability. Avoid mixing these styles (like2024-0315), as it is invalid. Our converter correctly outputs your choice of a valid, consistent format. - Incorrectly Handling Midnight and 24:00: While
24:00is valid in ISO 8601 to represent the exact end of a day (equivalent to00:00of the next day), it is often misunderstood and poorly supported by libraries. For maximum compatibility, using00:00for the start of a day is the safer, more widely accepted practice.
Frequently Asked Questions
What does the T in ISO 8601 format mean?
The "T" is a required literal separator between the date and time portions, preventing ambiguity. For example, in "2024-03-15T14:30:00Z", the T clearly separates the date (2024-03-15) from the time (14:30:00Z). This strict format ensures reliable parsing by all computer systems and APIs.
What does Z mean at the end of an ISO 8601 timestamp?
The "Z" stands for "Zulu time," which is equivalent to Coordinated Universal Time (UTC). A timestamp ending in Z (e.g., "2024-03-15T14:30:00Z") is explicitly in UTC. **Always include Z or a timezone offset (±HH:MM).** Omitting it creates ambiguous, non-compliant timestamps that can cause critical bugs in distributed systems and logs. Use the converter above to guarantee correct formatting.
Why does ISO 8601 use the YYYY-MM-DD format?
The YYYY-MM-DD format is internationally unambiguous, solving the confusion between MM/DD/YYYY (US) and DD/MM/YYYY (Europe). Its greatest technical advantage is that **lexicographical (alphabetical) sorting produces perfect chronological order**. This makes it ideal for database indexing, log file naming, and API responses where correct sort order is essential without complex parsing.
What does 'lexicographical sorting' mean for dates?
Lexicographical sorting means sorting text strings alphabetically. Because the ISO 8601 date structure begins with the year (YYYY), then month (MM), then day (DD), a simple alphabetical sort of these strings (e.g., in a database or filesystem) will automatically arrange them from earliest to latest—a key feature you are already ranking for in search.
Is 2024/03/15 a valid ISO 8601 format?
\**No. Using slashes (/) or dots (.) is a common mistake.** The ISO 8601 standard strictly defines hyphens as the separator for the extended date format (YYYY-MM-DD) and colons for time (HH:MM:SS). Formats like "2024/03/15" are not compliant and may fail in systems requiring strict validation. Our converter ensures correct, standard-compliant output.
What is the difference between 2024-12-01 and 2024-W48-7?
The first is a **calendar date** (December 1st, 2024). The second is a **week date**, representing the 7th day (Sunday) of the 48th week of 2024. ISO week numbering is used in specific industries like manufacturing and finance. For general purposes, use calendar dates to avoid confusion, as our tool can generate both.
How do I convert a local time to ISO 8601 with a timezone offset?
To represent a local time, use the ±HH:MM format after the time. For example, 10:30 AM in Pakistan Standard Time (UTC+5) becomes "2024-03-15T10:30:00+05:00". **Never omit the offset for local times.** This converter correctly formats times with their proper UTC offset to ensure global interoperability.