Category
Date & Time Tools & Calculators
Calendar-aware date and time utilities that handle leap years and month lengths correctly: date differences, age, business days, ISO week numbers, time zones, and durations.
Date and time tools here use the browser’s own calendar engine, so leap years, month lengths, and DST transitions are handled by the same rules your operating system follows: date differences, business days, ages, ISO week numbers, and timezone conversion.
Most used in Date & Time
Date Difference Calculator
Find the exact duration between two dates in days, weeks, months, and years — with leap years and month lengths handled correctly.
Age Calculator
Compute exact age in years, months, and days from a birth date — plus total days lived and a countdown to the next birthday.
Business Days Calculator
Count working days between two dates, or find the date N business days from today — with configurable weekends and holiday exclusion.
Week Number Calculator
Get the ISO-8601 week number for any date, plus the quarter and day of year — or list every week of a year with start dates.
Time Zone Converter
Convert times between any IANA time zones with full daylight-saving awareness, plus a side-by-side world clock for scheduling calls.
All Date & Time
Add or Subtract Days from Date
Add or subtract days, weeks, months, or years from any date — with correct end-of-month clamping (Jan 31 + 1 month = Feb 28/29).
Time Card Calculator
Enter a week of clock-in and clock-out times with unpaid breaks and get daily totals, overtime split, and decimal hours formatted for payroll.
Decimal Hours Calculator
Convert clock times (7:45) to payroll decimals (7.75) and back, with a reference table of the minute values that trip people up most often.
What each tool answers
- Date Difference — total days/months/years between dates, optionally excluding weekends for business-day counts.
- Age Calculator — exact age in years, months, and days, respecting leap-year birthdays (Feb 29 ages on Feb 28 or Mar 1 depending on locale convention — the tool states which it uses).
- Business Days Calculator — working days between dates; you choose which days are non-working.
- Timezone Converter — wall-clock times across zones, applying current DST rules for each.
Inclusive vs exclusive counting
The difference between Mar 1 and Mar 2 is 1 day if you count elapsed time, 2 days if both endpoints are included. Business-day calculators make this choice explicit; check which mode you are in before booking leave or setting deadlines — this single setting accounts for nearly all "the calculator is off by one" reports.
Common mistakes
- Crossing a DST change and expecting the hour count to match calendar days — a 23-hour or 25-hour day is correct, not a bug.
- Assuming ISO week 1 always starts January 1; it starts on the Monday of the year containing the first Thursday.
- Comparing times across zones using offsets that change seasonally — always convert rather than subtracting offsets by hand.