` Days Calculator — Days Between Dates & Add/Subtract Days | CalcPocket
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Days between dates & date arithmetic

Calculate the exact number of days between two dates with a full breakdown — or add and subtract years, months, weeks, and days from any starting date. Includes weekday counts, hours, and months elapsed.

Days between any two dates Add or subtract years, months, weeks Full breakdown (years, months, weeks) Weekdays & weekends count Total hours & minutes Direction-aware (past or future)

Days Calculator

Date difference & date arithmetic

Mode
Result
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Full Breakdown
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Years
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Months
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Weeks
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Total days
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Hours
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Minutes
Weekday Split
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Weekdays
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Weekends
Start
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End
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Days Calculator — Date Difference & Date Arithmetic

This free days calculator handles two of the most common date tasks: finding how many days separate two calendar dates, and finding what date results from adding or subtracting a duration from a starting date. Both modes account for leap years, month-length differences, and calendar edge cases automatically.

The result includes more than a single number — it shows the full breakdown in years, months, weeks, and days, plus total hours and a weekday/weekend split so you can plan projects, deadlines, and schedules accurately.

When to Use Each Mode

Days Between Two Dates

Use when you know both the start and end date and want to measure the gap. Common uses:

  • How many days until a vacation, event, or deadline
  • How long ago a past date was
  • Days elapsed in a project or subscription period
  • Age of a contract, warranty, or membership
  • Days between two historical dates
Add / Subtract from a Date

Use when you know a starting date and a duration and want to find the resulting date. Common uses:

  • What date is 90 days from today?
  • Find a payment due date 30 days after invoice
  • Calculate end of 3-month trial period
  • Find anniversary or milestone dates
  • Determine return/refund window deadlines

How Days Are Counted

The "days between" calculation uses a simple but important rule: it counts the number of full calendar days between the two dates. For most purposes, both the start and end dates are counted inclusively — but the convention varies by context:

ContextConventionExample
General date difference Exclusive of start, inclusive of end Jan 1 to Jan 5 = 4 days
Legal / contract periods Both dates inclusive Jan 1 to Jan 5 = 5 days
Event countdown (days until) Exclusive of today, inclusive of event Today to Jan 5 = days remaining
Days elapsed Inclusive of start, exclusive of end Jan 1 started, Jan 5 not yet complete = 4 days

This calculator uses the standard exclusive-start, inclusive-end convention (matching most date libraries and financial day-count conventions). Add 1 to the result if you need both dates included.

Leap Years & Month Lengths

The "add/subtract" mode uses calendar arithmetic rather than a fixed number of days per month or year. This means:

Adding 1 month Goes to the same day of the following calendar month. Jan 31 + 1 month = Feb 28 (or 29 in a leap year), not March 2.
Adding 1 year Goes to the same date one year later. Feb 29 + 1 year = Feb 28 (if next year is not a leap year).
Adding weeks & days These are exact: 1 week = 7 days always. Added after years and months are resolved.

Frequently Asked Questions

Select the "Days Between Dates" mode, enter your Start Date and End Date, then click Calculate. The result shows the total days, along with the breakdown in years, months, weeks, total hours, and a weekday/weekend split. The calculator works for both future and past dates.
Switch to "Add / Subtract from a Date" mode. Enter today's date in the Base Date field (or use the Today button), select Add, set Days to 90, and click Calculate. The result shows the exact date 90 days from now, plus the day of the week.
Yes. JavaScript's built-in Date object handles leap years automatically. Adding months and years uses calendar arithmetic — Feb 29 + 1 year becomes Feb 28 (or Feb 29 if the target year is a leap year). Day and week additions are always exact: 1 week = 7 days.
For "Days Between" mode, the calculator iterates through each day in the range and checks if it's Monday–Friday (weekday) or Saturday–Sunday (weekend). The totals are shown in the breakdown. Public holidays are not filtered — use the weekday count as a starting point and subtract holidays manually.
"Days Between" measures the gap between two known dates. "Add/Subtract" starts from one known date and finds the resulting date after applying a duration. They solve opposite problems: one measures, the other projects.
Yes. The calculator works for any two dates regardless of whether they're past, present, or future. If the end date is before the start date, the result is shown with a "Start date is after end date" note and the values are still calculated correctly.
The weekday count in the result gives you the number of Monday–Friday days between your dates. Subtract any public holidays that fall within the range to get the true working day count for your region.
Yes. For "days between" contract periods where both dates are inclusive, simply add 1 to the displayed result. For subscription renewals, use "Add/Subtract" mode: enter the start date, add the subscription term (e.g. 1 year or 30 days), and the result is your renewal date.

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Date & Time Calculators

The Days Calculator is part of CalcPocket's Date & Time cluster — tools for date arithmetic, scheduling, and time management.

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Days Calculator

Days between dates with full breakdown (years, months, weeks, weekdays, hours) plus add/subtract mode for date arithmetic.

days calculator days between dates date difference add days to date

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