Birthday Calculator
Enter your birthday to find your exact age, how many days until your next birthday, the day of the week you were born, and other fun facts.
Frequently Asked Questions
Exact age is calculated as years, months, and days from your birth date to today. It accounts for leap years and variable month lengths.
In a group of just 23 people, there's a 50% chance that two people share the same birthday. With 70 people, that probability rises to 99.9%.
How Date and Time Calculations Work
Calculating time differences, work hours, and date intervals requires handling the non-uniform nature of calendars — months have 28–31 days, leap years add a day, and daylight saving time shifts clocks by an hour. This calculator handles those complexities automatically so you get accurate results every time.
Common Time Calculation Formulas
- Time difference: Convert both times to total minutes from midnight, subtract, convert back
- Weekly work hours: Sum of daily hours; overtime typically kicks in above 8 hours/day or 40 hours/week (varies by state)
- Days between dates: Count calendar days inclusive or exclusive of start/end depending on context
- Business days: Subtract weekends and federal holidays from total calendar days
How to Use This Calculator
- Enter your start and end times or dates in the provided fields
- For work hours, enter daily clock-in and clock-out times for each day
- Include any unpaid break times to get accurate paid hours
- Click Calculate to see total hours, days, or the breakdown you need
Overtime Rules in the US
Under the Fair Labor Standards Act (FLSA), non-exempt employees must be paid 1.5× their regular rate for all hours over 40 in a workweek. Some states (California, Nevada, Alaska) have daily overtime rules — 1.5× after 8 hours in a single day. Always check your state labor law for the specific rules that apply to your situation.
Example: Weekly Timesheet
Mon–Fri: 8:00 AM – 5:00 PM with 30-min unpaid lunch = 8.5 hrs/day × 5 = 42.5 hours
Regular pay (40 hrs): 40 × hourly rate | Overtime (2.5 hrs): 2.5 × 1.5 × hourly rate