Next Day

Next Day - Problem

JavaScript Easy

Write code that enhances all Date objects such that you can call the date.nextDay() method on any date object and it will return the next day in the format YYYY-MM-DD as a string.

Your task is to modify the Date prototype to add a nextDay() method that correctly handles:

Regular day increments
Month boundaries (e.g., January 31 → February 1)
Year boundaries (e.g., December 31 → January 1 of next year)
Leap years (February 28/29 transitions)

The method should return a string in ISO date format (YYYY-MM-DD) representing the day immediately following the given date.

Input & Output

Example 1 — Regular Day Increment

$ Input: dateString = "2023-06-15"

› Output: "2023-06-16"

💡 Note: Simple case: June 15th becomes June 16th, no boundary crossing needed

Example 2 — Month Boundary

$ Input: dateString = "2023-01-31"

› Output: "2023-02-01"

💡 Note: End of January rolls over to beginning of February

Example 3 — Year Boundary

$ Input: dateString = "2023-12-31"

› Output: "2024-01-01"

💡 Note: New Year's Eve rolls over to New Year's Day of the next year

Constraints

Input date string is always in YYYY-MM-DD format
Year range: 1000 ≤ year ≤ 9999
Date represents a valid calendar date
Must handle leap years correctly

Visualization

Tap to expand

Asked in

G Google 25 a Amazon 20 M Microsoft 18 f Meta 15

The key insight is to leverage built-in date libraries rather than manually handling all edge cases. The optimal approach uses JavaScript's Date arithmetic with setDate(getDate() + 1) which automatically handles month boundaries, year rollovers, and leap years. Time: O(1), Space: O(1)

Common Approaches

✓ JavaScript Date Arithmetic

⏱️ Time: O(1) Space: O(1)

This approach leverages JavaScript's Date constructor and arithmetic. We create a Date object, add one day using setDate(), and let JavaScript handle all edge cases including leap years and month boundaries automatically.

Manual Date Calculation

⏱️ Time: O(1) Space: O(1)

This approach manually checks for month boundaries, leap years, and year boundaries. We increment the day and handle overflow cases by resetting day to 1 and incrementing month, then handle December overflow to next year.

JavaScript Date Arithmetic — Algorithm Steps

Create Date object from input string
Use setDate(getDate() + 1) to add one day
JavaScript automatically handles all overflow cases
Format result using toISOString() and extract date part

Visualization

Tap to expand

Step-by-Step Walkthrough

Create Date

new Date(dateString) parses input

Add Day

setDate(getDate() + 1) increments

Auto-Handle

JavaScript manages all overflows

Code -

solution.c — C

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

char* solution(char* dateString) {
    int year, month, day;
    sscanf(dateString, "%d-%d-%d", &year, &month, &day);
    
    // Days in each month
    int daysInMonth[] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
    
    // Check for leap year
    if ((year % 4 == 0 && year % 100 != 0) || (year % 400 == 0)) {
        daysInMonth[1] = 29;
    }
    
    // Increment day
    day++;
    
    // Check if day exceeds month limit
    if (day > daysInMonth[month - 1]) {
        day = 1;
        month++;
        
        // Check if month exceeds 12
        if (month > 12) {
            month = 1;
            year++;
        }
    }
    
    // Format result
    char* result = malloc(11);
    sprintf(result, "%04d-%02d-%02d", year, month, day);
    return result;
}

int main() {
    char dateString[20];
    fgets(dateString, sizeof(dateString), stdin);
    dateString[strcspn(dateString, "\n")] = 0;
    
    char* result = solution(dateString);
    printf("%s\n", result);
    free(result);
    
    return 0;
}

Time & Space Complexity

Time Complexity

⏱️

O(1)

Built-in Date operations are constant time

✓ Linear Growth

Space Complexity

O(1)

Only creates one Date object

✓ Linear Space

25.0K Views

Medium Frequency

~15 min Avg. Time

850 Likes

Ln 1, Col 1

Smart Actions

💡 Explanation

AI Ready

💡 Suggestion Tab to accept Esc to dismiss

// Output will appear here after running code

Code Editor Closed

Click the red button to reopen

Input & Output

Constraints

Visualization

Related Problems

Common Approaches

JavaScript Date Arithmetic — Algorithm Steps

Visualization

Code -

Time & Space Complexity

Select Compiler