日期推算
给任意日期加减天/周/月/年，得到结果日期与星期几；一键 +7/+30/+90/+365 天，算签证、倒计时、截止日都好用。
按公历（格里高利历）计算；月/年加减会按目标月份的实际天数自动收敛（如 1 月 31 日 +1 个月 = 2 月 28/29 日）。
中文介绍
办签证要算「停留期满 90 天是哪天」、订票要算「出发前 30 天抢票日」、项目要算「今天起 180 天的截止日」——这类「从某天起往后/往前推 N 天」的需求很常见。这个工具输入一个基准日期，加减任意数量的天、周、月、年，立刻给出结果日期和星期几，并内置 +7/+30/+90/+180/+365 天等常用快捷按钮。
全部在本地浏览器按公历计算，无需联网。
常见问题
「+1 个月」遇到 1 月 31 日会怎样？
按公历规则自动收敛到目标月的最后一天：1 月 31 日 +1 个月 = 2 月 28 日（闰年为 29 日）。同理 3 月 31 日 +1 个月 = 4 月 30 日。
怎么算「再过 90 天是哪天」？
基准日期留今天的默认值，运算选「加」、数量填 90、单位选「天」，点计算；或直接点快捷按钮 +90 天。
结果包含基准日期当天吗？
不包含。+1 天 = 明天的日期。若要算「从今天到某天共几天」，请用本站的「日期差计算」工具。
English
Working out "when does my 90-day stay end", "when should I book 30 days before departure", or "what's the deadline 180 days from now" all need adding or subtracting days from a date. Enter a base date, add or subtract any number of days, weeks, months or years, and get the resulting date and weekday instantly — with +7/+30/+90/+180/+365 quick buttons.
Everything runs locally in your browser using the Gregorian calendar.
FAQ
What happens to "Jan 31 + 1 month"?
It clamps to the last day of the target month: Jan 31 + 1 month = Feb 28 (Feb 29 in a leap year). Likewise Mar 31 + 1 month = Apr 30.
How do I find "the date 90 days from now"?
Leave the base date as today, choose Add, amount 90, unit days, and calculate — or just click the +90 quick button.
Does the result include the base date itself?
No. +1 day is tomorrow. To count days between two dates, use the site's "Days Between Dates" tool.