Date & Time Calculators
Professional date and time tools for calculating durations, business days, time zones, countdowns, and astronomical events. All calculations done instantly in your browser.
Complete Date & Time Calculation Suite
Date and time calculations are fundamental to planning, scheduling, and understanding temporal relationships. Whether you need to calculate business days for a deadline, find the duration between two events, or determine sunrise times for photography, our comprehensive calculator suite handles it all. Every calculation runs entirely in your browser with no data sent to servers, ensuring both privacy and instant results.
Calendar math is surprisingly complex. Different months have different lengths, leap years add February 29th, and time zones shift with daylight saving changes. Our calculators handle these edge cases automatically, supporting dates from year 1 to 9999 with proper handling of the Gregorian calendar system.
Days Between Dates & Duration Calculations
The days between dates calculator is our most popular tool, used millions of times for everything from pregnancy tracking to project planning. Enter any two dates and instantly see the duration in days, weeks, months, and years. The time duration calculator extends this to hours and minutes, perfect for tracking work hours, event lengths, and elapsed time.
Business Day Calculations
Business deadlines rarely fall on weekends or holidays. Our business days calculator counts only working days between dates, automatically excluding weekends and federal holidays for US, UK, Canada, and Australia. The business date calculator works in reverse, finding the exact date N business days from any starting point. Both tools are essential for project managers, legal professionals, and anyone working with contractual deadlines.
Time Zone Tools
In our globally connected world, time zone calculations are crucial for international business, remote work, and travel planning. Our time zone converter handles conversions between any world time zones, automatically adjusting for daylight saving time. The meeting planner takes this further, helping you find overlap in working hours across multiple time zones to schedule calls and meetings that work for everyone.
Age & Countdown Calculators
The age calculator provides exact age down to the day, along with fun facts like zodiac signs, generation labels, and upcoming milestones. The countdown calculator creates live countdowns to any future date, perfect for tracking time until holidays, birthdays, vacations, and deadlines. Both tools update in real-time to show current values.
Astronomical Calculators
Our sunrise and sunset calculator computes exact times for any location and date, including twilight phases and golden hour windows for photographers. The moon phase calculator shows the current lunar phase, illumination percentage, and upcoming full and new moon dates. These tools use established astronomical algorithms that provide accuracy within a few minutes of official times.
Special Date Tools
Find what day of the week any date falls on with the weekday calculator, or get ISO week numbers for business and project planning. The Roman numeral converter handles dates for formal documents and copyright notices. The date pattern calculator discovers interesting dates like palindromes and sequential number dates, perfect for planning memorable events.
All Date & Time Calculators
Date Calculator
Add or subtract days, weeks, months, years
Days Between Dates
Calculate days, weeks, months between dates
Time Duration Calculator
Calculate time between two times
Time Calculator
Add or subtract hours, minutes, seconds
Business Days Calculator
Count working days between dates
Business Date Calculator
Add or subtract business days
Weekday Calculator
Find the day of the week for any date
Week Number Calculator
Find ISO week number for any date
Roman Numeral Converter
Convert to and from Roman numerals
Age Calculator
Exact age with milestones & time alive
Date Pattern Calculator
Find palindrome & special dates
Countdown Calculator
Live countdown to any date
Time Zone Converter
Convert times across world time zones
Meeting Planner
Find best meeting times across zones
Sunrise & Sunset Calculator
Sunrise, sunset & day length times
Moon Phase Calculator
Current moon phase & full moon dates
Common Use Cases
🏢 Business & Finance
Calculate payment due dates, contract deadlines, invoice terms, and project milestones using business day calculations.
✈️ Travel Planning
Convert time zones for flights, find sunrise/sunset at destinations, and count down to your departure date.
📸 Photography
Plan golden hour and blue hour shoots with precise sunrise/sunset times and twilight calculations for any location.
🌐 Remote Work
Schedule meetings across time zones, find working hour overlap, and track hours for distributed teams.
🎂 Personal Events
Calculate age, count down to birthdays and anniversaries, find special dates, and track milestones.
📋 Project Management
Track sprint durations, calculate delivery dates, find week numbers for reporting, and plan releases.
Date & Time Calculator FAQs
How do you calculate business days between dates?
Business days exclude weekends (Saturday and Sunday) and federal holidays. Our calculator counts only Monday through Friday, with options to exclude holidays for different countries. The start date is typically not counted, so Monday to Friday equals 4 business days.
What is ISO week numbering?
ISO 8601 defines week 1 as the week containing the first Thursday of the year. Weeks run Monday to Sunday. Most years have 52 weeks, but some have 53. This standard is widely used in business and project management across Europe and internationally.
How accurate are sunrise/sunset calculations?
Our sunrise and sunset calculator uses standard astronomical algorithms that provide accuracy within 1-2 minutes for most locations. Factors like local terrain, atmospheric conditions, and altitude can affect actual observed times slightly.
Do time zone conversions handle daylight saving time?
Yes, our time zone converter automatically adjusts for daylight saving time based on the date selected. This includes handling the dates when DST begins and ends, which vary by country and region.
How long is a lunar cycle?
The lunar cycle (synodic month) is approximately 29.53 days. This is the time from one new moon to the next. Our moon phase calculator uses this cycle to determine the current phase and predict upcoming full and new moons.
What date range do these calculators support?
Our calculators support dates from year 1 to year 9999 in the Gregorian calendar. They properly handle leap years, month lengths, and calendar edge cases. For historical dates before 1582 (when the Gregorian calendar was adopted), results use proleptic Gregorian dating.
Are calculations done on your servers?
No, all calculations run entirely in your browser using JavaScript. No data is sent to our servers. This ensures complete privacy and provides instant results without network latency. Your data never leaves your device.
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