Days Since and Date Difference Calculator
Count days since a past date, compare any two calendar dates, or calculate age from a birth date.
Related guides: How to Calculate the Number of Days Between Two Dates
Calculate days since a date
Enter the past date as the start and today as the end to calculate elapsed days. The result also shows approximate weeks and a calendar-style years, months, and days breakdown. For the number of days between any two dates, replace today with your chosen end date.
The elapsed total excludes the start date. Add one only when your rule explicitly counts both endpoints. The calculator compares calendar dates; it does not add a number of days to a date, skip weekends or holidays, or apply a business-calendar policy.
How this tool helps
Date differences come up in project planning, school assignments, invoices, event countdowns, subscriptions, and personal records. This calculator gives a quick human-readable difference between two calendar dates and includes an age mode for date-of-birth checks.
How to use it
- Choose standard difference mode when you already have a start date and an end date.
- Use age mode when the first date is a birthday and the second date should be today.
- Review both the exact day count and the year-month-day breakdown, since different tasks prefer different wording.
Practical tips
- Calendar months vary in length, so month and year breakdowns are best treated as human-readable estimates.
- For legal, payroll, medical, or compliance deadlines, confirm the counting rule required by the organization.
- If the end date is before the start date, swap the dates or treat the result as time remaining in reverse.
FAQ
Does it include the end date?
The main day count measures elapsed time between dates; add one day manually if your task counts both endpoints.
What is age mode for?
Age mode fills the end date with today and labels the result as an age-style calculation.
Does time zone affect the result?
The tool normalizes dates at local midnight, which is suitable for ordinary calendar comparisons.
Related tools
Calculate months between two dates
To calculate the number of months between two dates, enter the start and end dates above. The calculator shows the difference in years, months, and days. For partial months, it counts complete months plus the remaining days as a fraction.
Common uses: project timelines, lease durations, subscription periods, age calculations, and contract terms. The tool handles leap years and varying month lengths automatically. For business days only, exclude weekends and holidays manually from the result.