Date & Calendar Calculator
Look up ISO week numbers, find the day of year, check leap years, convert Julian Day Numbers and decode Unix timestamps into human-readable dates.
Results
What week number is it? Is this year a leap year? What is Julian Day Number 2460677? These tools answer the date and calendar questions that come up in business invoicing (week numbers), agriculture and weather (day of year), astronomy (Julian dates), software development (Unix timestamps) and general curiosity (leap years). Every tool works for any date, past or future.
Frequently asked questions
Enter today's date in the Week Number Calculator. ISO weeks are numbered 1-53 and start on Monday. Week 1 contains January 4. Many businesses use week numbers for invoicing, reporting and sprint planning.
The Day of Year Calculator shows the ordinal day (1-366). January 1 = day 1, July 1 = day 182. Used in agriculture, meteorology and logistics for date-independent scheduling.
The Leap Year Checker tells you instantly. The rule: divisible by 4, except centuries unless also divisible by 400. So 2024 is a leap year, 2100 is not, 2000 was.
A Unix timestamp counts seconds since January 1, 1970. The Unix Timestamp Converter decodes any timestamp to a human-readable date. Developers encounter these in APIs, databases, logs and JWT tokens.
JDN is a continuous day count since January 1, 4713 BC, used in astronomy. The Julian Day Converter also shows Modified Julian Date (used in satellite operations) and days from the J2000.0 epoch.
All date & calendar tools
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