Validate a Calendar Date

Need to verify if a list of dates like 2024-02-29 or 2023-04-31 are actually valid calendar dates? The Validate a Calendar Date Tool checks every line of input and tells you whether each one matches a real calendar date. You can paste in the data or import a file, and the results will update live no reloads needed.

It uses the YYYY-MM-DD format and compares each line against the real calendar, catching things like leap years and invalid dates such as April 31st. You can also switch between emoji-style or text-style markers for the results.

Paste your input above or import a file below.
No file chosen
Supported file types: .txt, .csv, .log
Total items: 0
Options
Trim whitespace
Ignore blank lines
Show only invalid dates

How to Use:

  1. Paste your dates (formatted like 2024-01-15) into the Input Dates box.
  2. Or click Choose File to upload a .txt, .csv, or .log file.
  3. In the Options panel:
    • Toggle Trim whitespace to clean each line.
    • Enable Ignore blank lines to skip empties.
    • Toggle Show only invalid dates to focus on problems.
    • Choose Emoji or Text for your result style.
  4. Check the Validation Results box for live feedback.
  5. Use Copy Output or Export to File to save the results.
  6. Hit Clear All to reset everything and start fresh.

What Validate a Calendar Date Tool can do:

  • Checks if each YYYY-MM-DD date is valid on the calendar
  • Flags invalid entries like 2023-02-29 or 2023-04-31
  • Lets you toggle between emoji markers or plain text
  • Ignores blanks and trims extra spaces if you want
  • Supports pasted text or file-based input
  • Shows a live count of the validated lines

Example:

Input:

2024-02-29
2023-04-31
2022-12-25
2023-02-29
2025-01-01

Output (Emoji mode):

2024-02-29 ✅
2023-04-31 ❌
2022-12-25 ✅
2023-02-29 ❌
2025-01-01 ✅

Output (Text mode):

2024-02-29 valid
2023-04-31 invalid
2022-12-25 valid
2023-02-29 invalid
2025-01-01 valid

Common Use Cases:

This tool is ideal for cleaning up date-based datasets, checking exported reports, validating form submissions, or ensuring accurate calendar input. Instead of manually scanning or guessing, you can paste your list and get instant validation with clear results.

Useful Tools & Suggestions:

If you’re building dates manually, Generate Valid Calendar Dates makes a great testbed. And when you want to catch issues, Generate Invalid Calendar Dates helps you spot what doesn’t pass validation.

Related Tools