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ISO 8601 Date Formatter
Format any date and time as an ISO 8601 string. Enter year, month, day, hour, minute, second and get the properly formatted ISO date string.
Formatted Output⧉
2026-03-12T14:30:00Z
Selected format: extended
Extended ISO⧉
2026-03-12T14:30:00Z
Full date-time with separators
Basic ISO⧉
20260312T143000Z
Compact form without separators
Date Only⧉
2026-03-12
Calendar date portion only
Time Only⧉
14:30:00Z
Time portion with offset
UTC Equivalent⧉
2026-03-12T14:30:00Z
Converted to Coordinated Universal Time
Ordinal Date⧉
2026-071
Day 71 of 365
ISO Week Date⧉
2026-W11-4
Week 11, day 4 of week
Year Progress
Day 71/365
19.5%
Common year (365 days) | UTC offset: Z
ISO 8601 Format Reference
| Format | Example | Common Use |
|---|---|---|
| Extended Date-Time | 2026-03-12T14:30:00Z | APIs, databases, JSON |
| Basic Date-Time | 20260312T143000Z | File names, compact logs |
| Date Only | 2026-03-12 | Date fields, reports |
| Time Only | 14:30:00+00:00 | Time-of-day values |
| Week Date | 2026-W11-4 | Scheduling, fiscal weeks |
| Ordinal Date | 2026-071 | Julian day, scientific logs |
| With Offset | 2026-03-12T09:30:00-05:00 | Local-time context |
| UTC (Zulu) | 2026-03-12T14:30:00Z | Universal reference |
Planning notes, formulas, and examples
About the ISO 8601 Date Formatter
The ISO 8601 Date Formatter generates properly formatted ISO 8601 date-time strings from individual date and time components. ISO 8601 is the international standard for date and time representation, universally used in APIs, databases, data interchange, and technical documentation.
The format follows the pattern YYYY-MM-DDTHH:mm:ssZ, where T separates date and time, and Z indicates UTC. For example, 2026-02-08T14:30:00Z represents February 8, 2026 at 2:30 PM UTC. This unambiguous format eliminates confusion caused by regional date formats like MM/DD/YYYY vs DD/MM/YYYY.
This calculator lets you enter each component separately and generates the correctly formatted string, including validation of month and day ranges. It's invaluable for developers building APIs, data engineers formatting records, and anyone who needs to produce standards-compliant date strings.
When This Page Helps
ISO 8601 is the standard date format for APIs, databases, and data interchange. Manually constructing these strings is easy to get wrong because of zero-padding requirements and separator rules. This formatter generates correct ISO strings so your dates stay standards-compliant.
How to Use the Inputs
- Enter the year (e.g., 2026).
- Enter the month (1–12).
- Enter the day (1–31, validated per month).
- Enter the hour, minute, and second (all optional, default to 0).
- The calculator generates the full ISO 8601 formatted string.
- Copy the result to use in APIs, code, or documentation.
Formula used
ISO 8601 Format: YYYY-MM-DDTHH:mm:ssZ
Where:
YYYY = four-digit year
MM = two-digit month (01–12)
DD = two-digit day (01–31)
HH = two-digit hour (00–23)
mm = two-digit minute (00–59)
ss = two-digit second (00–59)
T = date-time separator
Z = UTC timezone designatorExample Calculation
Result: 2026-02-08T14:30:00Z
The components year=2026, month=02, day=08, hour=14, minute=30, second=00 are assembled into the ISO 8601 string 2026-02-08T14:30:00Z. The T separates date from time, and Z indicates UTC.
Tips & Best Practices
- Always zero-pad single-digit months, days, hours, minutes, and seconds.
- The T separator between date and time is required in the standard.
- Z means UTC. For local time with offset, use +HH:MM or −HH:MM instead.
- Date-only format (YYYY-MM-DD) is also valid ISO 8601.
- Use ISO 8601 in APIs to avoid ambiguity between US (MM/DD) and European (DD/MM) formats.
- Many databases accept ISO 8601 strings directly for date/time columns.
Why ISO 8601 Matters
Regional date formats cause errors worldwide. Americans write March 4 as 03/04, while Europeans write it as 04/03. ISO 8601's YYYY-MM-DD format eliminates this confusion entirely. Major technology companies, international standards bodies, and governments recommend ISO 8601 for all date interchange.
Extended Format Options
Beyond the basic date-time format, ISO 8601 supports: week dates (2026-W06-1 for Monday of week 6), ordinal dates (2026-039 for the 39th day of 2026), durations (P3Y6M4DT12H30M5S), and time intervals (start/end or start/duration).
Adoption in Technology
ISO 8601 is used by HTML5 date inputs, XML Schema, JSON APIs, SQL databases (as text representation), and most programming languages' standard libraries. When building any system that stores or transmits dates, ISO 8601 should be the default format.
Sources & Methodology
Last updated:
Frequently Asked Questions
ISO 8601 is an international standard for representing dates and times. It was first published in 1988 and uses the format YYYY-MM-DDTHH:mm:ssZ. Its unambiguous format makes it the preferred choice for data interchange between systems worldwide.
ISO 8601 eliminates ambiguity in date representation. Is 03/04/2026 March 4th or April 3rd? Depends on regional conventions. But 2026-03-04 is always March 4th. This clarity is critical when systems exchange data across regions.
The letter T is a separator between the date portion (YYYY-MM-DD) and the time portion (HH:mm:ss). It indicates where the date ends and the time begins. Some systems accept a space instead of T, but T is the standard.
Z stands for Zulu time, which is another name for UTC. When a date-time string ends with Z, it means the time is in UTC. If a local time offset is needed, replace Z with +HH:MM or −HH:MM.
Yes. ISO 8601 allows date-only strings like 2026-02-08, week dates like 2026-W06, and ordinal dates like 2026-039. The full date-time format is just one of several valid representations.
JSON does not have a native date type, so dates are typically serialized as ISO 8601 strings. This is the de facto standard in REST APIs, GraphQL, and most modern web services. JavaScript's JSON.stringify uses ISO 8601 for Date objects.
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