Fix date format interpretation for dd/mm/yy format

[Berkaysuozer]

Fix date format interpretation for dd/mm/yy format

Issue

When using the dd/mm/yy date format, the component was incorrectly interpreting date strings. Specifically, when a date string like 09/10/2025 (representing 9th October 2025) was passed to the formatValue() function, it would incorrectly return 10/09/2025 (10th September 2025).

This issue only occurred:

• When using the specific dd/mm/yy date format
• When the day value was less than 12 (since it could be misinterpreted as a month)
• When manually entering/predefined dates (not when selecting directly from the datepicker)

Root Cause

JavaScript's default date parsing interpreted the date string using the American format (mm/dd/yyyy) regardless of the format specified in dateFormat. This caused ambiguous dates where the day is ≤12 to be interpreted incorrectly.

Solution

Added specific handling for the dd/mm/yy format to correctly parse date strings using the European format (day first, then month). The solution:

1. Checks if the format is specifically dd/mm/yy
2. Verifies the input matches a date string pattern with slashes
3. Manually parses the date components in the correct order
4. Creates a valid Date object with the properly ordered components

if (this.dateFormat === 'dd/mm/yy' && /^\d{1,2}\/\d{1,2}\/\d{2,4}$/.test(value)) {
   const parts = value.split('/');
   const day = parseInt(parts[0], 10);
   const month = parseInt(parts[1], 10) - 1; // JS months are 0-based
   const year = parts[2].length === 2 ? 2000 + parseInt(parts[2], 10) : parseInt(parts[2], 10);
   
   const date = new Date(year, month, day);
   
   // Verify the date is valid
   if (!isNaN(date.getTime())) {
       return this.formatDate(date, this.dateFormat);
   }
}

Before the fix, some date strings were misinterpreted due to incorrect handling of date formats. Specifically, dates in DD/MM/YYYY format were being mistakenly parsed as MM/DD/YYYY.

Example

Before the fix:

• Input: "09/10/2025"
• Output: "10/09/2025"

After the fix:

• Input: "09/10/2025"
• Output: "09/10/2025"

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Test Cases

Input	Expected Output	Result Before Fix	Result After Fix
09/10/2025	09/10/2025	10/09/2025	09/10/2025
05/06/2025	05/06/2025	06/05/2025	05/06/2025
12/10/2025	12/10/2025	10/12/2025	12/10/2025
15/06/2025	15/06/2025	15/06/2025	15/06/2025

---

Summary

The fix ensures that date strings are correctly interpreted according to the DD/MM/YYYY format. This prevents confusion and potential data errors for users.

[cagataycivici]

Unable to merge as the PR strictly checks for a specific format. Also there is no such thing as date string, default values should be Dates, so please make sure to feed the default values as Dates, not String.