Generate Invalid Calendar Dates

The Generate Invalid Calendar Dates Tool helps you create lists of impossible or malformed dates for testing and validation purposes. You can generate dates like 2024-02-30, 2023-13-01, or 00/00/0000, choose the output format, limit the year range, and optionally shuffle the output.

This tool is perfect for QA teams, developers, and anyone testing systems that need to handle or reject invalid calendar input. The Generate Invalid Calendar Dates Tool updates live and supports copy and export options.

Total items: 0
Options
Bad days (e.g. Feb 30)
Bad months (e.g. 2023-13-01)
Shuffle output

How to Use:

  1. Select the Start Year and End Year for which you want to generate invalid dates.
  2. Choose the Date Format:
    • YYYY-MM-DD
    • DD/MM/YYYY
    • MM/DD/YYYY
  3. Use the toggles to choose what types of invalid dates to include:
    • Bad days: dates like 2024-02-30 or 2024-04-31
    • Bad months: dates with month values like 00 or 13
    • Include zero date: the common invalid 0000-00-00
  4. Optionally toggle Shuffle Output to randomize the list.
  5. Click Generate to build the list. The output appears instantly and flashes when updated.
  6. Use Copy Output or Export to File to save your results.
  7. Use Clear All to reset everything.

What Generate Invalid Calendar Dates Tool can do:

This tool generates a list of syntactically correct but semantically invalid calendar dates:

  • Invalid days of month (e.g., April 31, Feb 30)
  • Invalid months (e.g., 00, 13)
  • Zero values (0000-00-00)
  • Customizable by year range, format, and order

It ensures comprehensive coverage for date validation testing.

Example:

Start Year: 2023
End Year: 2025
Format: MM/DD/YYYY

Output:
02/30/2023
13/01/2023
04/31/2024
00/15/2025
00/00/0000

Common Use Cases:

Use this tool to test date validation systems, simulate user error input, stress test APIs or date parsers, or build automated test cases for web forms and database constraints. It’s a must-have for QA engineers and devs building robust date-handling features.

Useful Tools & Suggestions:

To explore what actually does work, Generate Valid Calendar Dates is a good contrast. And if you want to throw even more unpredictability into the mix, Add Errors to Calendar Dates makes things extra messy in just the right way.

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