✅ 校验日历日期Validate Calendar Date
逐行检查是否为有效的公历日期 YYYY-MM-DD（0001–9999 年），每行给出结论和原因。本地处理。Check line by line whether each entry is a valid Gregorian YYYY-MM-DD date (years 0001–9999), with a verdict and reason per line. Processed locally.
使用说明与常见问题How-to & FAQ
「校验日历日期」是什么？What is the Validate Calendar Date tool?
逐行检查是否为有效的公历日期 YYYY-MM-DD（0001–9999 年），每行给出结论和原因。本地处理。Check line by line whether each entry is a valid Gregorian YYYY-MM-DD date (years 0001–9999), with a verdict and reason per line. Processed locally.
如何使用「校验日历日期」？How do I use the Validate Calendar Date tool?
每行输入一个要检查的日期，下方逐行显示“有效”或“无效”及原因。Enter one date per line and each line gets a valid or invalid verdict with the reason below.
可以一次检查多个日期吗？Can I check several dates at once?
可以，每行一个，空行跳过；每一行都单独给出“有效/无效”和原因，多行时前面标出行号。Yes, one per line with blank lines skipped. Every line gets its own valid/invalid verdict and reason, prefixed with its line number when there are several.
1582 年的空缺日期算有效吗？Are the missing days of 1582 valid?
按外推格里高利历算有效，但会注明：1582-10-05 至 1582-10-14 在 1582 年改历的国家（如意大利、西班牙）并不存在；其他国家改历更晚。They count as valid on the proleptic Gregorian calendar, with a note that 1582-10-05 to 1582-10-14 never happened in countries that switched in 1582 (such as Italy and Spain); other countries switched later.
怎样判断 2 月 29 日是否有效？How does it decide whether February 29 is valid?
仅闰年接受 02-29：能被 4 整除且不能被 100 整除，或能被 400 整除（1900-02-29 无效，2000-02-29 有效）。02-29 is accepted only in leap years: divisible by 4 and not by 100, or divisible by 400 (1900-02-29 is invalid, 2000-02-29 valid).
用的是哪种历法、支持哪些年份？Which calendar and years are supported?
按外推格里高利历（现行公历规则向前沿用）计算，年份为 0001–9999，输出一律为 4 位年份的 YYYY-MM-DD。1582-10-05 至 1582-10-14 在 1582 年改历的国家并不存在，这里仍按外推格里高利历处理。The proleptic Gregorian calendar (today's rules applied backwards) for years 0001 to 9999, always written as YYYY-MM-DD with a 4-digit year. 1582-10-05 to 1582-10-14 never happened in countries that switched calendars in 1582; they are still handled on the proleptic Gregorian calendar here.
和时区有关吗？Do time zones matter?
无关。「校验日历日期」只做时长或日期格式的换算，不读取设备时间，时区和夏令时不影响结果。No. The Validate Calendar Date tool only converts durations or date formats and never reads the device clock, so time zones and daylight saving time do not affect the result.
「校验日历日期」免费吗？需要注册吗？Is the Validate Calendar Date tool free? Do I need an account?
「校验日历日期」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 Validate Calendar Date tool is completely free with no sign-up or install and works on phones and desktops; what you enter is processed only in your browser.