日期加减计算器
基于开始日期自由加上或减去年、月、周、天数以得出结果日期。
Add Days to Date
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计算原理
- Units are applied to the start date in a fixed order (years, then months, then weeks, then days) and the exact composition is echoed with the result so the arithmetic is auditable.
- Months and years clamp at month ends: Jan 31 + 1 month is Feb 28 (or Feb 29 in a leap year), and Feb 29 + 1 year is Feb 28. When clamping happens, the note says so.
- Days and weeks are pure calendar shifts anchored to noon UTC, immune to daylight saving and midnight rollover.
使用提示
- Negative values subtract; for example, days = −10 moves the date back ten days. The direction is shown in the composition line.
- Empty unit fields are treated as 0; you only need the units you are actually changing.
- Result dates are real calendar dates; the weekday is shown so you can sanity-check the result at a glance.
相关工具
常见问题解答
What happens to January 31 plus one month?
February has no 31st, so the result is clamped to the last day of February (28, or 29 in leap years). The page shows the clamping note whenever it applies.
Can I subtract instead of add?
Yes, enter a negative number or use the subtract option. The operation and direction are always shown in the result line.
Are the units combined?
Yes: years, months, weeks and days are applied in that order to the start date, and the exact composition is echoed in the result so the arithmetic is auditable.