📅 日期加减天数Add Days to a Date

使用说明与常见问题How-to & FAQ

「日期加减天数」是什么？What is the Add Days to a Date tool?

在给定日期上加（或减）整天数；天数留空视为 0。本地处理。可设置「日期」、「天数（可负）」。Add (or subtract) whole days from a date; leave days blank for 0. Processed locally. Settings: Date, Days (may be negative).

如何使用「日期加减天数」？How do I use the Add Days to a Date tool?

在「日期加减天数」中，填写「日期」、「天数（可负）」等参数，结果会随输入实时计算并显示在下方。In the Add Days to a Date: Fill in "Date", "Days (may be negative)"; results are recalculated instantly as you type.

时区或夏令时会影响结果吗？Do time zones or daylight saving time affect the result?

不会。本页只按日历整天加减，不涉及具体时刻，所以跨越夏令时切换或月末、闰年时结果都是正确的日期，例如 2024-02-28 加 1 天得到 2024-02-29。No. It adds whole calendar days with no time of day involved, so crossing a daylight-saving change, a month end or a leap day still gives the right date; for example, 2024-02-28 plus 1 day is 2024-02-29.

天数可以留空吗？必须是整数吗？Can days be blank? Must it be an integer?

可以留空，按 0 天（日期不变）。须为整数（可为负）；小数会提示须为整数。绝对值超过 10,000,000 会提示过大，避免日历溢出。Blank means 0 days (date unchanged). It must be a whole number (negatives allowed); a decimal gets "must be an integer". Absolute values above 10,000,000 are rejected as too large so the calendar cannot overflow.

能举个计算实例吗？Can you show a worked example?

例如在「日期加减天数」中填 日期 = 2026-10-20，天数（可负） = 7，结果区显示：结果日：2026-10-27For example, entering Date = 2026-10-20, Days (may be negative) = 7 in the Add Days to a Date gives: Result date: 2026-10-27

哪些输入会被检查？Which inputs are validated?

「日期加减天数」会检查这些输入——「天数（可负）」：可留空；绝对值超过 10¹⁵ 的数也会被拒绝。不符合时结果区显示具体提示，不会给出数字。The Add Days to a Date checks its inputs — "Days (may be negative)": optional; numbers above 10¹⁵ in absolute value are rejected too. When a value fails, the result area names the problem instead of showing a number.

有哪些选项可以调整？What options can I adjust?

「日期加减天数」的设置：「日期」默认 2026-10-20；「天数（可负）」默认 7。每次生成结果都按当前设置处理。Settings in the Add Days to a Date — "Date" default 2026-10-20; "Days (may be negative)" default 7. The result always uses the current settings.

「日期加减天数」免费吗？需要注册吗？Is the Add Days to a Date free? Do I need an account?

「日期加减天数」完全免费，无需注册或安装，打开网页即可使用，手机和电脑都能用；输入的内容只在你的浏览器本地处理。The Add Days to a Date is completely free with no sign-up or install and works on phones and desktops; what you enter is processed only in your browser.