如何计算Add or Subtract Days from Date
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An add or subtract dates calculator computes a new date by adding or subtracting a specified number of days, weeks, or months from a starting date. Used for deadlines, scheduling, and date planning.
公式
result_date = start_date ± days (accounting for month/year boundaries)
- start
- Start date (date) — Base date (YYYY-MM-DD)
- days
- Days to add/subtract (days) — Positive = future, negative = past
- result
- Result date (date) — The calculated date
分步指南
- 1For days: add/subtract directly from the date
- 2For weeks: multiply by 7 then add/subtract days
- 3For months: adjust the month field and handle month-end overflow
- 4JavaScript Date handles leap years automatically
例题解析
输入
Jan 15 + 90 days
结果
April 15 (or 16 in leap year)
输入
Mar 31 + 1 month
结果
April 30 (month-end handling)
输入
Today − 30 days
结果
Date 30 days ago
常见问题
How does the calculator handle month boundaries?
It automatically adjusts for varying month lengths and leap years. Adding 30 days to Jan 1 correctly lands on Jan 31.
Can I subtract dates to go backward in time?
Yes, use a negative number. Subtracting 10 days from Mar 15 = Mar 5. The calculator respects month/year boundaries.
What about leap seconds or daylight saving?
Calendar calculations ignore leap seconds and DST. They operate on calendar dates, not absolute time.
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