Date Add Subtract Calculator
Add or subtract days, weeks, months and years to any date. Add months to date or add years to any starting date - and instantly see the result date in all formats. Find what date is 30, 60, 90 or any number of days from today. Business days mode skips weekends. Use as a date calculator to add days to date, subtract days from date, or find what date is N days from now. Multiple output formats ready to copy. No login required.
Add or Subtract Days, Weeks, Months & Years - With Business Days Mode
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Everything the Date Add Subtract Calculator Does
How to Add or Subtract Days from a Date
Date Calculator: LazyTools vs Competitors
Most date calculators only add or subtract days from today. LazyTools lets you start from any date, combine years + months + weeks + days simultaneously, and use business days mode.
| Feature | LazyTools | timeanddate.com | calculator.net | Google search |
|---|---|---|---|---|
| Add/subtract from any date | Yes | Yes | Yes | Today only |
| Add years + months + days together | Yes (simultaneous) | Yes | Days only | Days only |
| Business days mode | Yes (Mon-Fri) | Yes | No | No |
| Multiple output formats | Yes (5 formats) | 1 format | 1 format | 1 format |
| ISO week number in result | Yes | Yes | No | No |
| Quick preset buttons | Yes (8 presets) | No | No | No |
| Correct month-end handling | Yes | Yes | Variable | Variable |
| No login required | Yes | Yes | Yes | Yes |
Date Add Subtract: Complete Reference
Date arithmetic is used in legal deadlines, financial calculations, project management, shipping estimates and everyday planning. The key complexity is that months have different lengths and years have leap days, so simple day counting often gives wrong results when working with months and years.
| Common query | Days to add | Use case |
|---|---|---|
| 7 days from today | 7 | One week deadline, weekly recurring events |
| 14 days from today | 14 | Two weeks notice, fortnight payment terms |
| 30 days from today | 30 | Net-30 invoice terms, 1 month estimate |
| 60 days from today | 60 | Net-60 invoice terms, 2 month estimate |
| 90 days from today | 90 | Quarterly deadline, 3 month estimate |
| 100 days from today | 100 | 100-day plan milestones |
| 6 months from today | 180-184 | 6-month review, half-year anniversary |
| 1 year from today | 365-366 | Annual renewal, 1-year warranty |
How to add days to a date correctly
Adding days to a date is straightforward: each day increments the calendar by exactly 24 hours. The complication arises with daylight saving time (DST) changes in local time zones. This calculator uses UTC internally to avoid DST-boundary errors - a common bug in date calculators that use local time, where adding 30 days across a DST boundary gives a result that is one hour off, occasionally appearing as the wrong day in certain timezones.
How to add months to a date
Adding months to a date requires special handling for month-end dates. When you add 1 month to 31 January, there is no 31 February, so the result is the last day of February (28 in a regular year, 29 in a leap year). This calculator always clamps to the last valid day of the result month rather than rolling over into the next month, which is the standard expected behaviour. Adding 1 month to 30 January gives 28 February (not 2 March).
What date is 90 days from today
The date that is 90 days from today changes every day. Use the Days from Today tab and enter 90 to get today's specific answer. 90 days is a common deadline period: in the UK and US, many contract notice periods are 90 days. VAT and tax return periods are often 90 days. Clinical trial follow-up periods commonly use 30, 60 or 90 day intervals. The 90-day rule in US immigration also uses calendar days.
Business days calculator: add working days to a date
The business days calculator mode adds working days (Monday to Friday) only, skipping every Saturday and Sunday. Adding 10 business days to a Monday means counting 5 days in the first week and 5 days in the second week, landing on a Friday. This is different from adding 14 calendar days (which would also be a Monday). Business day calculations are used in: invoice payment terms (net 10, net 20 business days), legal notice periods, shipping and delivery estimates, and financial settlement periods (T+2 settlement = 2 business days after trade date).
Date arithmetic in different contexts
Different industries define "month" and "day" differently. In banking, some calculations use a 30/360 day count convention where every month is treated as exactly 30 days and every year as 360 days. In contract law, months are calendar months (from the 15th of one month to the 15th of the next). In shipping, transit time is usually calendar days. This calculator uses calendar months and calendar days, which matches everyday usage. For specialised financial calculations, check the specific day count convention specified in the contract.
Subtract days from a date: practical examples
Subtracting days is as useful as adding: find the start date of a project given its deadline and duration, calculate when to send a reminder before a payment due date, find the date 90 days before year-end for tax planning, or calculate the last day of a warranty period from today. Enter the end/deadline date as the start date, choose Subtract, and enter the number of days to go back.