Date Format Converter
Convert a list of dates between declared formats, ISO dates and offset timestamps. Keep invalid rows and ambiguous month/day values visible.
Starts with an editable example. Replace the dates and rules with your own.
Your calculation
Ready when you are
Choose your dates.
Select your counting rules and calculate.
Calculation details
| Step | Value |
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How to use this calculator
Paste one value per line. Select the exact input format, desired output format and time zone for date-only inputs or local output.
Dates are parsed strictly without guessing month/day order. RFC 3339 inputs require Z or a numeric offset and support milliseconds. Date-only inputs use midnight in the selected zone; a missing or repeated midnight needs a valid resolution.
A worked example
With MM/DD/YYYY input, 11/04/2026 becomes 2026-11-04. The impossible date 02/30/2026 remains an error row.
Does 03/04/2026 mean March 4 or April 3?
The declared input format decides. The report flags dates that could be read both ways so you can check the source.
Which calendar and years are supported?
Each result states its calendar, time scale, precision and supported range. Batch converters accept up to 100 nonempty input lines and retain invalid rows. Copy, CSV and print include the calculation rules. Calendar downloads appear when a result contains dated events. Calculations run in your browser; no reminders or jobs are scheduled.
What happens to my dates?
Calculations run on your device. Saving a calculation is optional and keeps it in this browser. A setup link contains the dates and settings you entered; anyone with the link can read them. Use one tab per saved calculator. Clear saved data from Privacy & settings.