Add or subtract days, weeks, months, and years from any date. Calculate the difference between two dates. Find business days and Australian public holidays.
Use the first tool below to add or subtract a number of years, months, weeks or days from any starting date — handy for deadlines, notice periods and expiry dates. Use the second tool to find the exact difference between two dates in years, months, days and business days. Both handle month-length and leap-year edge cases automatically, so "31 January plus 1 month" correctly lands on 28 February rather than overshooting into March.
| Unit | Value |
|---|
Adding a period to a date sounds simple until months of different lengths get involved. Days and weeks are easy — every day is exactly 86,400 seconds, so adding 7 days always lands on the same weekday one week later. Months and years are different: they don't have a fixed length, so "add 1 month" has to mean "move to the same day-of-month next month," and when that day doesn't exist (adding a month to 31 January, for example), the result has to be clamped to the last valid day of the target month rather than silently rolling forward into the following month.
| Count type | Includes | Typically used for |
|---|---|---|
| Calendar days | Every day, including weekends and public holidays | Tenancy notice periods, employment notice under the National Employment Standards, most contract terms |
| Business days | Monday–Friday only | Some court filing deadlines and contract clauses that explicitly say "business days" |
| Business days excl. public holidays | Monday–Friday, minus the relevant state's public holidays | Legislation and contracts that specify "excluding public holidays" — public holidays vary by state, so this calculator's business-day count is a Monday–Friday baseline only |
When calculating deadlines, contract periods, or legal notice periods in Australia, it's important to know whether "days" means calendar days or business days — the Interpretation Act 1901 (Cth) sets out how time periods are counted in Commonwealth legislation, and most state Acts have equivalent provisions. Business days in Australia exclude weekends and public holidays; because public holidays vary by state and territory, always check your specific state's calendar for an exact business-day count when a deadline is time-critical.
| Mistake | Why it matters |
|---|---|
| Assuming every month is 30 days | Real months range from 28 to 31 days — "add 60 days" and "add 2 months" give different results |
| Not clamping day-of-month when adding months | 31 January + 1 month should be 28 February, not a rolled-over date in March |
| Confusing calendar days with business days in a deadline | A "5 day" notice period served on a Thursday can mean very different actual dates depending on which definition applies |
| Forgetting leap years | Every 4th year (except century years not divisible by 400) has 366 days — this shifts multi-year date-difference calculations by a day or more |
This calculator has two modes. The first adds or subtracts a period of time from a starting date — enter the start date, select Add or Subtract, and enter the number of years, months, weeks, and days. The second calculates the difference between two dates — enter both dates and see exactly how many years, months, days, weeks, and total days apart they are, including business days.
| Situation | How to use it |
|---|---|
| ATO tax return deadline (31 Oct) | Date difference from 30 June to 31 Oct = 123 days |
| Lease notice period (28 days) | Add 28 days to today to find the earliest vacate date |
| Settlement period (6 weeks after contract) | Add 42 days (6 weeks) to contract signing date |
| Statutory warranty period (2 years) | Add 2 years to purchase date to find warranty expiry |
| Probation period end (3 or 6 months) | Add 3 or 6 months to employment start date |
When counting notice periods and legal deadlines it matters whether "days" means calendar days or business days. Most Australian tenancy notice periods use calendar days. Employment notice periods under the National Employment Standards use calendar days. Court filing deadlines and some contract provisions specify business days — which exclude weekends and the public holidays specific to the relevant state.
For example: a 5 business day notice period served on a Thursday would not expire until the following Thursday or Friday (depending on whether any public holidays fall in between) — not the following Tuesday as calendar-day counting would suggest.
Beginner:
31 March 2026 (March has 31 days, so day 30 lands on the 31st).
3 months exactly (92 calendar days).
Advanced:
30 April 2026 — April only has 30 days, so the result is clamped rather than overflowing into May.
20 business days (4 full weeks).
Because February doesn't have 31 days, the result is clamped to the last valid day of the target month (28th, or 29th in a leap year) rather than rolling over into March. This matches how most people intuitively expect "add a month" to behave.
Adding days or weeks is a fixed-length operation — every day is exactly 24 hours, so the math is straightforward addition. Adding months or years is calendar-aware: it moves to the same day-of-month in a later month, which can require clamping if that day doesn't exist in the target month (see above).
365 days (366 in a leap year). The financial year runs 1 July to 30 June. Use the difference calculator above to find exactly how many days remain to 30 June — useful for timing CGT events and super contributions.
Calendar days include weekends and public holidays. Business days, as counted by this tool, exclude Saturday and Sunday only — it does not exclude state-specific public holidays, since these vary by location. Most Australian tenancy and employment notice periods use calendar days.
Typically 30–90 days from contract, with 42 days (6 weeks) being the most common default. Shorter settlements are possible if both parties are ready; longer ones are common when buyers need additional finance time. Add 42 days to a contract date above to estimate a standard settlement date.
Yes. Both the add/subtract tool and the difference tool use the actual number of days in each month and year, including 29 February in leap years, so multi-year and multi-month calculations that cross a leap year are accurate.