Get the correct century from 2-digit year date value - JavaScript?

When working with 2-digit year values, you need to determine which century they belong to. A common approach is using a pivot year to decide between 19XX and 20XX centuries.

Example

Following is the code −

const yearRangeValue = 18;
const getCorrectCentury = dateValues => {
    var [date, month, year] = dateValues.split("-");
    var originalYear = +year > yearRangeValue ? "19" + year : "20" + year;
    return new Date(originalYear + "-" + month + "-" + date).toLocaleDateString('en-GB')
}; 
console.log(getCorrectCentury('10-JAN-19'));
console.log(getCorrectCentury('10-JAN-17'));
console.log(getCorrectCentury('10-JAN-25'));

Output

10/01/2019
10/01/2017
10/01/2025

How It Works

The pivot year (18 in this example) determines the century assignment:

• Years > 18 (19, 20, 21, etc.) are treated as 19XX (1919, 1920, 1921)
• Years ? 18 (00-18) are treated as 20XX (2000-2018)

Alternative Approach with Current Year

const getCorrectCenturyDynamic = (dateString) => {
    var [date, month, year] = dateString.split("-");
    var currentYear = new Date().getFullYear() % 100; // Get 2-digit current year
    var fullYear = +year > currentYear ? "19" + year : "20" + year;
    return new Date(fullYear + "-" + month + "-" + date).toLocaleDateString('en-GB');
};

console.log(getCorrectCenturyDynamic('10-JAN-19'));
console.log(getCorrectCenturyDynamic('10-JAN-50'));

Output

10/01/2019
10/01/1950

Conclusion

Use a pivot year strategy to convert 2-digit years to 4-digit years. Choose your pivot based on your data's expected range for accurate century determination.