Date Add/Subtract
Add or subtract days, weeks, months, quarters, or years to/from any date. Find the resulting date instantly with day of week, days between, and quarter.
Add or Subtract Days, Weeks, Months, Years
Find future or past dates instantly. Supports days, weeks, months, quarters, and years. Perfect for deadlines, contracts, and planning.
๐ Quick Examples โ Click to Load
Start Date
Operation
Amount & Unit
Duration Breakdown
Result Year Type
๐ Calculation Breakdown
For educational and informational purposes only. Verify with a qualified professional.
๐ Key Takeaways
- โข Add or subtract days, weeks, months, quarters, or years to any date
- โข 1 quarter = 3 months (Q1: JanโMar, Q2: AprโJun, Q3: JulโSep, Q4: OctโDec)
- โข Month arithmetic handles variable lengths (e.g., Jan 31 + 1 month = Feb 28/29)
- โข Leap years add Feb 29; the calculator automatically accounts for this
๐ก Did You Know?
๐ How Date Add/Subtract Works
Date arithmetic requires careful handling of variable month lengths and leap years. Days and weeks are straightforward (add/subtract milliseconds). Months and years require special logic to handle edge cases like Jan 31 + 1 month.
Days & Weeks
JavaScript Date objects handle day arithmetic natively. Adding 7 days = 1 week. The calculator converts weeks to days before applying.
Months & Quarters
Adding months uses "same day" logic: Jan 31 + 1 month = Feb 28 (or 29 in leap years). Quarters are 3-month increments.
๐ฏ Expert Tips
๐ก Contract Deadlines
90-day notice periods, 30-day return windows, and 1-year renewals โ use this calculator to find exact end dates.
๐ก Fiscal Planning
Add 1 quarter for quarterly reviews. Add 1 year for annual planning. Combine with our Business Days Calculator for workday counts.
โ๏ธ Comparison
| Feature | This Calculator | Excel | Manual |
|---|---|---|---|
| Add days/weeks/months/years | โ | โ | โ ๏ธ Error-prone |
| Quarter support | โ | โ ๏ธ Formula needed | โ |
| Day of week | โ | โ ๏ธ Formula | โ |
| Leap year detection | โ | โ ๏ธ | โ |
| Days/weeks between | โ | โ | โ |
| Charts & copy/share | โ | โ | โ |
โ Frequently Asked Questions
How do I add 90 days to a date?
Enter your start date, select Add, enter 90, and choose Days. The result shows the exact date 90 days later, plus day of week and days between.
What is a quarter in date terms?
1 quarter = 3 months. Q1 is JanโMar, Q2 AprโJun, Q3 JulโSep, Q4 OctโDec. Adding 1 quarter moves the date forward 3 months.
Does it handle leap years?
Yes. Adding months across February in a leap year correctly uses Feb 29. The result also shows whether the result year is a leap year.
What happens with Jan 31 + 1 month?
The result is Feb 28 (or Feb 29 in a leap year). Same-day logic is used: we aim for the same day of month, clamping to the last day if the month is shorter.
Can I subtract dates?
Yes. Select Subtract and enter the amount. The result will be a date in the past.
How many days is 52 weeks?
52 weeks = 364 days (52 ร 7). So adding 52 weeks is 1 day short of a full year. For exactly 1 year, use the Years unit.
What date range is supported?
The calculator supports dates from year 1 to 275760. For most practical uses (1900โ2100), all calculations are accurate.
How do I find a date 6 months ago?
Enter today (or your reference date), select Subtract, enter 6, and choose Months. The result is exactly 6 months before.
๐ Date Facts by the Numbers
๐ Official Data Sources
โ ๏ธ Disclaimer: This calculator uses the Gregorian calendar. For legal, tax, or contractual deadlines, verify with official sources. Not legal or financial advice.
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