12 to 24 Hour Converter
12-hour time (e.g. 2:30 PM) → 24-hour time
24 to 12 Hour Converter
24-hour time (e.g. 14:30) → 12-hour time
Add Days to Date
Start date, Days to add → Result date
Age Calculator
Date of birth → Age
Birthday Countdown
Your birthday → Days until birthday
Business Days Calculator
Start date, End date → Working days
Date Calculator
Start date, End date → Total days
Date Difference Calculator
Start date, End date → Total days
Days Between Dates
Start date, End date → Total days
Leap Year Checker
Year → Result
Military Time Converter
12-hour time (e.g. 2:30 PM) → Military (24-hour) time
Ovulation Date Calculator
First day of last period, Cycle length (days) → Ovulation date
Pregnancy Week Calculator
First day of last period → Gestational weeks
Retirement Date Calculator
Date of birth, Retirement age → Retirement date
Subtract Days from Date
Start date, Days to subtract → Result date
Working Days Calculator
Start date, End date → Working days
What the date and time tools cover
Calendar arithmetic is easy to get wrong by a day. These tools do it properly: age in years, months and days; the difference between two dates; adding or subtracting a number of days; business days between two dates with weekends excluded; a birthday or retirement date countdown; leap year checks; and conversion between 12-hour and 24-hour clock notation.
Months have unequal lengths, February changes size every four years with two exceptions per four centuries, and daylight-saving shifts make a day 23 or 25 hours long once a year. The calculators work in calendar units where the question is about calendar units (an age is not total days divided by 365) and in raw days where that is the honest answer. Each page says which.
Things the tools cannot know
- Public holidays vary by country and by year, so the business-day count excludes weekends only.
- Time-zone rules change by jurisdiction. A countdown is measured against your device's clock and its idea of local midnight.
- Pregnancy and ovulation dates use standard averages (a 28-day cycle, 40 weeks from the last period) that many people do not match.