年龄是怎么算出来的
日期相减听起来简单，但闰年、每月天数不同和时区让它变复杂。这个计算器按真实日历走：先算整年，再算剩余月，最后算天——所以 2 月 29 日出生的人在平年也能得到正确年龄。一切都在浏览器中运行，出生日期不会发送到任何地方。
常见用途
求职申请和政府表格常要求填写“截至某日”的年龄——用截止日期字段即可。家长用它查入学年龄门槛，HR 核验最低年龄要求，好奇的人则喜欢看自己的年龄以秒为单位跳动。
常见问题
How accurate is this age calculator?
Fully — it accounts for leap years and varying month lengths, computing down to the second based on your device clock.
What if I was born on February 29?
In non-leap years the calculator treats March 1 as the anniversary for year counting, the common legal convention in most places.
Can I calculate age at a future or past date?
Yes. Leave “Age at date” empty for today, or pick any date — for example, how old you'll be when a contract starts.
Is my birth date stored?
No. The calculation happens locally in JavaScript. Nothing is uploaded or saved.
Why does my age differ from another calculator?
Some calculators ignore leap days or count months as 30 days. This one walks the real calendar, which is the correct method.