Tools for working with dates and times: convert between date formats (ISO 8601, RFC 2822, Unix timestamp, and more), calculate business days between two dates, look up week numbers and day-of-year, add or subtract days/weeks/months/years from a date, and count down to any event in real time.
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Format dates with custom patterns (YYYY-MM-DD, etc.). Supports ISO 8601, RFC formats, and custom templates.
Create a countdown to any future date and time. Shows days, hours, minutes, and seconds remaining.
Calculate the date after adding business days, excluding weekends and Japanese public holidays (2020–2026).
Find the ISO week number and day of year for any date. Shows start and end date of the week.
Add or subtract days, weeks, months, or years to a date. Calculates the resulting date instantly.
Everything about ISO 8601 — the YYYY-MM-DDTHH:mm:ssZ format, timezone offsets (Z vs +00:00), durations, week numbers, and how to use it in JavaScript, Python, PHP, SQL, and HTML.
Date formatting confusion is surprisingly common. Learn the most widely used date formats — ISO 8601, RFC 2822, US-style MM/DD/YYYY — what each means, when to use them, and how to convert between them without bugs.
"Ships in 3 business days" — when does it actually arrive? Learn what business days mean, how to count them correctly, why holidays complicate things, and how to calculate them automatically.
Need to know how many days until a deadline, birthday, or event? Learn how to calculate remaining days manually, with spreadsheet formulas, and using browser tools — plus tips for deadline management.
The Business Days Calculator is the most-used tool here — enter two dates and instantly get the number of working days between them, excluding weekends. The Date Add Calculator is great for computing deadlines like "90 days from today."