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Complete Guide to Time Conversion

Master time conversion for software development, project management, and everyday calculations with practical examples and best practices.

Quick Reference Table

From	To	Formula	Example
Weeks	Days	× 7	2 weeks = 14 days
Days	Hours	× 24	3 days = 72 hours
Hours	Minutes	× 60	2 hours = 120 minutes
Minutes	Seconds	× 60	5 minutes = 300 seconds
Seconds	Milliseconds	× 1000	3 seconds = 3000 ms
Days	Milliseconds	× 86,400,000	1 day = 86,400,000 ms

Real-World Examples for Developers

Example 1: JavaScript setTimeout

Setting a timeout for 5 minutes:

// Convert 5 minutes to milliseconds
const fiveMinutes = 5 * 60 * 1000; // = 300,000 ms

setTimeout(() => {
    console.log('5 minutes have passed!');
}, fiveMinutes);

Pro tip: Use our time converter to quickly get the millisecond value.

Example 2: API Rate Limiting

Limiting API calls to 100 requests per hour:

// Calculate milliseconds between requests
const requestsPerHour = 100;
const millisecondsPerHour = 60 * 60 * 1000; // = 3,600,000
const delayBetweenRequests = millisecondsPerHour / requestsPerHour;

console.log(delayBetweenRequests); // 36,000 ms (36 seconds)

Example 3: Cache Expiration

Setting cache to expire after 24 hours:

// Python example
cache_duration_seconds = 24 * 60 * 60  # 86,400 seconds
cache.set('user_data', data, timeout=cache_duration_seconds)

// JavaScript example
const cacheDurationMs = 24 * 60 * 60 * 1000;  // 86,400,000 ms
localStorage.setItem('timestamp', Date.now() + cacheDurationMs);

Project Management Time Calculations

Converting Sprint Duration

A 2-week sprint in different time units:

Days: 2 weeks × 7 = 14 calendar days
Work days: 2 weeks × 5 = 10 business days
Work hours: 10 days × 8 = 80 person-hours
Total hours: 14 days × 24 = 336 hours

💡 Tip: Always clarify whether you're using calendar days (7 per week) or business days (5 per week) when estimating project timelines.

Resource Allocation Example

A project requires 240 person-hours. With a team of 3 developers working 8-hour days:

Total capacity per day: 3 people × 8 hours = 24 person-hours/day
Days needed: 240 ÷ 24 = 10 work days
Weeks needed: 10 ÷ 5 = 2 weeks

Common Programming Scenarios

Database Query Optimization

Finding Records from Last 7 Days

-- SQL example
SELECT * FROM orders
WHERE created_at >= NOW() - INTERVAL 7 DAY;

-- Or using timestamp comparison (in seconds)
WHERE created_at >= UNIX_TIMESTAMP() - (7 * 24 * 60 * 60);

7 days = 604,800 seconds = 604,800,000 milliseconds

Performance Benchmarking

Measuring Function Execution Time

// JavaScript
const start = performance.now();
expensiveFunction();
const end = performance.now();
const durationMs = end - start;
const durationSeconds = durationMs / 1000;

console.log(`Executed in ${durationSeconds.toFixed(3)} seconds`);

IoT and Embedded Systems

Sensor Polling Intervals

Temperature sensor reading every 5 minutes with data transmission every hour:

Reading interval: 5 minutes = 300 seconds = 300,000 ms
Transmission interval: 1 hour = 3,600 seconds = 3,600,000 ms
Readings per transmission: 60 ÷ 5 = 12 readings

Arduino Example

// Reading every 5 minutes (300,000 ms)
const unsigned long READING_INTERVAL = 5UL * 60 * 1000;

void loop() {
    static unsigned long lastReading = 0;
    unsigned long now = millis();
    
    if (now - lastReading >= READING_INTERVAL) {
        readTemperature();
        lastReading = now;
    }
}

Common Mistakes to Avoid

⚠️ Mistake 1: Confusing seconds with milliseconds in JavaScript

// WRONG - will timeout immediately
setTimeout(callback, 5); // Only 5 milliseconds!

// CORRECT - 5 seconds
setTimeout(callback, 5000); // 5,000 milliseconds = 5 seconds

⚠️ Mistake 2: Not accounting for business days

When a client says "2 weeks," they might mean:

10 business days (5 days × 2 weeks)
14 calendar days (7 days × 2 weeks)

Always clarify!

⚠️ Mistake 3: Floating point precision errors

// May have precision issues with very large numbers
const nanoseconds = seconds * 1000000000;

// Better: Use BigInt for very large values
const nanoseconds = BigInt(seconds) * 1000000000n;

Best Practices

1. Use Constants for Clarity

// Good: Self-documenting code
const MILLISECONDS_PER_SECOND = 1000;
const SECONDS_PER_MINUTE = 60;
const MINUTES_PER_HOUR = 60;
const HOURS_PER_DAY = 24;

const oneDayInMs = HOURS_PER_DAY * MINUTES_PER_HOUR * 
                   SECONDS_PER_MINUTE * MILLISECONDS_PER_SECOND;

// Bad: Magic numbers
const oneDayInMs = 86400000; // What is this?

2. Comment Your Conversions

// Cache expires after 7 days (604,800,000 ms)
cache.set('data', value, 604800000);

// Even better with a descriptive constant
const SEVEN_DAYS_MS = 7 * 24 * 60 * 60 * 1000;
cache.set('data', value, SEVEN_DAYS_MS);

3. Validate User Input

function convertHoursToSeconds(hours) {
    if (typeof hours !== 'number' || hours < 0) {
        throw new Error('Hours must be a positive number');
    }
    return hours * 60 * 60;
}

Time Conversion Cheat Sheet

Common Conversions to Memorize

1 minute: 60 seconds = 60,000 milliseconds
1 hour: 60 minutes = 3,600 seconds = 3,600,000 milliseconds
1 day: 24 hours = 1,440 minutes = 86,400 seconds = 86,400,000 milliseconds
1 week: 7 days = 168 hours = 604,800 seconds
30 days: 720 hours = 43,200 minutes = 2,592,000 seconds

Handy Shortcuts

To convert hours to seconds: multiply by 3,600
To convert days to milliseconds: multiply by 86,400,000
To convert weeks to hours: multiply by 168
To find milliseconds between requests: divide total ms by number of requests

💡 Pro Tip: Bookmark our time converter tool for instant conversions while coding. No need to break your flow!

Additional Resources

Frequently Asked Questions - Common time conversion questions answered
Time Converter Tool - Instant conversions between all time units
About Time Converter - Learn more about our tool and mission

Practice Problems

Test your time conversion skills:

How many milliseconds are in 2.5 hours? (Answer: 9,000,000 ms)
An API allows 1000 requests per day. How many seconds between requests? (Answer: 86.4 seconds)
A cache expires in 3 days. Express this in seconds. (Answer: 259,200 seconds)
Convert 500,000 milliseconds to minutes. (Answer: 8.33 minutes)

Use our time converter to check your answers!