Time & Date Tools
Free date and time calculators. Count days between dates, find business days, convert across timezones, and calculate your exact age. Results update as you type.
Days Between Dates
Calculate the exact difference between any two dates in days, weeks, hours, and calendar months.
Business Days Calculator
Count working days between two dates, automatically excluding weekends and US public holidays.
Add / Subtract Days
Find a future or past date by adding or subtracting any number of days from a starting date.
Timezone Converter
See a single moment in time displayed across 22 major world timezones simultaneously.
Age Calculator
Find your exact age in years, months, and days — plus total days lived and your next birthday countdown.
Why Date and Time Calculations Are Surprisingly Complex
Calendar arithmetic sounds simple until you account for leap years (every 4 years, except centuries, except every 400 years), daylight saving time transitions (which vary by country, region, and year), and time zone offsets that change for political reasons. The IANA Time Zone Database — maintained by ICANN and used by every major operating system and programming language — currently tracks over 600 time zones with their full historical transition data, because countries regularly change their time zone rules.
Business Days vs. Calendar Days
The difference between calendar days and business days matters in legal contracts, financial settlements, and project planning. A 30-day calendar period may contain only 20-22 business days after excluding weekends. Adding federal holidays (which vary by jurisdiction — the US has 11, the UK has 8, Canada has 9) reduces this further. Our business days calculator uses the US federal holiday schedule published by the Office of Personnel Management (OPM).
UTC and Why Software Uses It
Coordinated Universal Time (UTC) is the global time standard, defined by the International Telecommunication Union (ITU) and maintained by atomic clocks. All time zones are expressed as UTC offsets (e.g., UTC-5 for US Eastern Standard Time). Software stores timestamps in UTC and converts to local time for display — this avoids the midnight-rollover bugs and DST ambiguity that arise when storing local times. When our timezone converter shows UTC, it is showing the unambiguous canonical form of that moment in time.
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