Age Calculator Guide: How Exact Age Is Computed
Calculating someone's age sounds trivial — just subtract the birth year from the current year, right? But that rough method is often off by a year. A precise age calculator accounts for months, days, and leap years to give you the exact span between two dates.
The Correct Method
Subtract days first (borrowing from months if needed), then months (borrowing from years), then years — just like long subtraction, but on a calendar.
Example: if today is August 7, 2026 and your birthday is March 15, 1995, your exact age is 31 years, 4 months, and 23 days. Simple year subtraction (2026 − 1995 = 31) would have been correct only if today were on or after March 15.
Leap Years and February 29
Leap years add a day every four years (with exceptions for century years not divisible by 400). This matters for people born on February 29 — in non-leap years their "birthday" is usually observed on February 28 or March 1. Our calculator handles this edge case automatically.
The same date-arithmetic logic powers our Date Calculator (add/subtract days) and Time Duration Calculator.
Total Days, Weeks, and Hours
Age isn't just years — sometimes you need the total span in another unit. The calculator also reports your age in total days, weeks, months, and even hours, which is useful for milestone tracking ("I've been alive 10,000 days!") or scientific contexts.
Put It Into Practice
Enter any birthdate and a target date to see the exact age broken down into years, months, and days — plus the totals.
年龄计算器指南：如何精确计算你的年龄
计算一个人的年龄听起来很简单——只需从当前年份减去出生年份，对吧？但这种粗略的方法通常会差一年。精确的年龄计算器会考虑月份、日期和 leap years，从而给出两个日期之间的确切时间跨度。
正确的计算方法
先减去日期（如有需要从月份借位），再减去月份（从年份借位），最后减去年份——就像长减法一样，但是在日历上进行。
示例：如果今天是 2026 年 8 月 7 日，你的生日是 1995 年 3 月 15 日，那么你的确切年龄是 31 年 4 个月零 23 天。简单的年份相减（2026 − 1995 = 31）只有在今天是 3 月 15 日或之后才是正确的。
Leap Years 与 2 月 29 日
Leap years 每四年增加一天（但对于不能被 400 整除的世纪年份有例外）。这对 2 月 29 日出生的人很重要——在非闰年，他们的"生日"通常在 2 月 28 日或 3 月 1 日庆祝。我们的计算器会自动处理这种边缘情况。
相同的日期算术逻辑也驱动着我们的日期计算器（加/减天数）和时间跨度计算器。
总天数、周数和小时数
年龄不仅仅是年——有时你需要以其他单位表示总跨度。计算器还会以总天数、周数、月份甚至小时数报告你的年龄，这对里程碑追踪（"我已经活了 10,000 天！"）或科学场景很有用。
动手实践
输入任何出生日期和目标日期，查看以年、月、日分解的确切年龄——以及总计数值。