Date Arithmetic

Add and subtract time from dates

BeginnerTopic: Date/Time Programs

JavaScript Date Arithmetic Program

This program helps you to learn the fundamental structure and syntax of JavaScript programming.

// Method 1: Add/subtract days
function addDays(date, days) {
    const result = new Date(date);
    result.setDate(result.getDate() + days);
    return result;
}

function subtractDays(date, days) {
    return addDays(date, -days);
}

const today = new Date();
console.log('Today:', today);
console.log('Tomorrow:', addDays(today, 1));
console.log('Yesterday:', subtractDays(today, 1));

// Method 2: Add/subtract months
function addMonths(date, months) {
    const result = new Date(date);
    result.setMonth(result.getMonth() + months);
    return result;
}

console.log('Next month:', addMonths(today, 1));
console.log('Last month:', addMonths(today, -1));

// Method 3: Add/subtract years
function addYears(date, years) {
    const result = new Date(date);
    result.setFullYear(result.getFullYear() + years);
    return result;
}

console.log('Next year:', addYears(today, 1));

// Method 4: Add/subtract hours
function addHours(date, hours) {
    const result = new Date(date);
    result.setHours(result.getHours() + hours);
    return result;
}

console.log('In 2 hours:', addHours(today, 2));

// Method 5: Add/subtract minutes
function addMinutes(date, minutes) {
    const result = new Date(date);
    result.setMinutes(result.getMinutes() + minutes);
    return result;
}

console.log('In 30 minutes:', addMinutes(today, 30));

// Method 6: Using timestamps
function addTime(date, milliseconds) {
    return new Date(date.getTime() + milliseconds);
}

console.log('Add 1 day (ms):', addTime(today, 24 * 60 * 60 * 1000));
console.log('Add 1 hour (ms):', addTime(today, 60 * 60 * 1000));

// Method 7: Date difference
function dateDifference(date1, date2) {
    const diff = Math.abs(date1 - date2);
    const days = Math.floor(diff / (1000 * 60 * 60 * 24));
    const hours = Math.floor((diff % (1000 * 60 * 60 * 24)) / (1000 * 60 * 60));
    const minutes = Math.floor((diff % (1000 * 60 * 60)) / (1000 * 60));
    return { days, hours, minutes };
}

const date1 = new Date('2024-01-01');
const date2 = new Date('2024-01-15');
console.log('Difference:', dateDifference(date1, date2));

Output

Today: 2024-01-15T10:30:45.123Z
Tomorrow: 2024-01-16T10:30:45.123Z
Yesterday: 2024-01-14T10:30:45.123Z
Next month: 2024-02-15T10:30:45.123Z
Last month: 2023-12-15T10:30:45.123Z
Next year: 2025-01-15T10:30:45.123Z
In 2 hours: 2024-01-15T12:30:45.123Z
In 30 minutes: 2024-01-15T11:00:45.123Z
Add 1 day (ms): 2024-01-16T10:30:45.123Z
Add 1 hour (ms): 2024-01-15T11:30:45.123Z
Difference: { days: 14, hours: 0, minutes: 0 }

Understanding Date Arithmetic

Date arithmetic manipulates dates.

Methods

•setDate/setMonth/setFullYear

•setHours/setMinutes/setSeconds

•Using timestamps

Adding Time

•Days: setDate(getDate() + n)

•Months: setMonth(getMonth() + n)

•Years: setFullYear(getFullYear() + n)

•Hours/Minutes: setHours/getMinutes

Subtracting

•Use negative values

•Or subtract from timestamp

Date Difference

•Calculate milliseconds

•Convert to days/hours/minutes

•Handle timezones

Best Practices

•Create new Date objects

•Don't mutate original

•Handle month/year boundaries

•Use timestamps for precision

Let us now understand every line and the components of the above program.

Note: To write and run JavaScript programs, you need to set up the local environment on your computer. Refer to the complete article Setting up JavaScript Development Environment. If you do not want to set up the local environment on your computer, you can also use online IDE to write and run your JavaScript programs.

Compare Dates

Format Date and Time