Antwort: Geben Sie ein Geburtsdatum ein und der Altersrechner gibt Ihr genaues Alter in Jahren, Monaten und Tagen zurück – plus die Gesamtzahl der gelebten Wochen, Tage und Stunden sowie einen Countdown bis zu Ihrem nächsten Geburtstag.
Ein Altersrechner rechnet Ihr Geburtsdatum in genaue Jahre, Monate und verstrichene Tage um und zählt optional bis zu Ihrem nächsten Geburtstag herunter.
Berechnen Sie das genaue Alter anhand des Geburtsdatums
Age is calculated as the time between your date of birth and the target date. The calculator counts whole years first, then whole months, then the leftover days — the same convention used on official forms in most Western countries. Each culture may count age differently: in the traditional Korean system, for example, a person is considered one year old at birth and gains a year at New Year rather than on their birthday, and traditional age reckoning is still commonly quoted in everyday conversation. For legal purposes — driving, voting, contracts, retirement — jurisdictions almost always use the completed-years convention this tool follows.
Under the hood, the math is straightforward but has one wrinkle: months have unequal lengths. When the target date's day-of-month is earlier than the birth day-of-month, the calculator borrows days from the previous month, using that month's actual length. That is why "one month" can mean 28, 29, 30, or 31 days depending on where the period falls, and why age expressed as years, months, and days is more precise than a single day count alone.
People ask for age in surprising units. A newborn's parent wants weeks; an insurance actuary wants days; a demographer wants decimal years. The table below shows the same four birth dates converted across units, computed against January 1, 2027. Leap-year birthdays follow the common legal convention: when February 29 does not exist in a year, the birthday is treated as falling on March 1 in some jurisdictions and February 28 in others, so the "next birthday" shown is the nearest of the two.
| Geburtsdatum | Alter am 1. Januar 2027 | Gesamtzahl der gelebten Tage | Tage bis zum nächsten Geburtstag |
|---|---|---|---|
| 1. Januar 1990 | 37 Jahre, 0 Monate, 0 Tage | 13.514 | 0 |
| 15. Juni 1990 | 36 Jahre, 6 Monate, 17 Tage | 13.349 | 165 |
| 31. Dezember 1995 | 31 J. 0 Mo. 1 T | 11.324 | 364 |
| 29. Februar 2000 | 26 Jahre, 10 Monate, 3 Tage | 9,803 | 424 (der nächste 29. Februar ist 2028) |
| 4. Juli 2005 | 21 Jahre, 5 Monate, 28 Tage | 7,851 | 184 |
Total days lived is simply the difference between the two dates, and each figure above was checked by counting the intervening leap years (1992, 1996, 2000, 2004, and every fourth year after) that add one extra day each. The "days to next birthday" column counts from January 1, 2027, which is why the January 1 birthday lands on 0.
The Gregorian calendar, introduced by Pope Gregory XIII in 1582, averages 365.2425 days per year — close to the tropical year of roughly 365.2422 days. That near-match is why the calendar stays aligned with the seasons over centuries, but the fractional day is also why any "years lived" figure rounded to whole days is only exact to the day, not the hour. This calculator also reports age in hours, which is convenient for newborns and for anyone who enjoys seeing a very large number grow in real time: a 37-year-old has lived through roughly 324,000 hours, and the count ticks up every hour without respect to birthdays.
Time zones add a final layer of subtlety. Dates are compared as calendar dates, not instants, so the result can differ by one day depending on where in the world you stand when you ask. For everyday purposes — forms, milestone birthdays, school enrollment cutoffs — the calendar-date convention this tool uses is the one that matters.
Beyond curiosity, exact age calculations gate real decisions. School enrollment cutoffs typically require a child to reach a given age on or before a specific date, and parents planning ahead check the boundary months in advance. Retirement systems, from Social Security in the United States to state pension schemes elsewhere, key benefits to completed age on particular dates — off-by-one-day errors here change when the first payment lands. Immigration forms, driver's license applications, insurance policies, and age-restricted purchases all ask for completed age as of a stated date, which is exactly what the age-at-date field computes.
Genealogy researchers use the same arithmetic in reverse: given an age recorded on a census or gravestone and the date of the record, they estimate a birth year by subtraction, allowing a year of slack for rounding. HR departments verify employment eligibility the same way. Whenever a document says "must be 18 years of age on or before," the honest check is completed years between the two dates — never rounding up.
Wie viele Tage bin ich alt?Geben Sie Ihr Geburtsdatum ein und lassen Sie „Alter am Datum“ auf „heute“ stehen; Der Rechner zeigt die Gesamtzahl der Tage sowie Jahre, Monate und Tage an.
Ändert ein Schalttag-Geburtstag mein gesetzliches Alter?Nein. Sie beenden immer noch jedes Jahr am 29. Februar ein Lebensjahr oder, in Nicht-Schaltjahren, an dem Ersatzdatum, das Ihre Gerichtsbarkeit festlegt, und Ihr Alter in vollendeten Jahren erhöht sich wie üblich einmal pro Jahr.
Warum unterscheidet sich mein Alter in einem anderen Land um einen Tag?Weil der Rechner Kalenderdaten vergleicht und derselbe Zeitpunkt auf unterschiedliche Daten in unterschiedlichen Zeitzonen fällt, wenn die lokalen Uhren Mitternacht markieren.
Was ist der Unterschied zwischen dem vollendeten Alter und dem Abrechnungsalter?Das vollendete Alter zählt nur volle Jahre seit der Geburt – der westliche Rechtsstandard –, während traditionelle Abrechnungssysteme bei eins beginnen und sich an einem Gruppendatum wie Neujahr erhöhen können.
Kann ich das Alter zu einem vergangenen oder zukünftigen Zeitpunkt berechnen?Ja; Stellen Sie „Alter am Datum“ auf ein beliebiges Datum ein, und alle Zahlen – Jahre, Monate, Tage, Stunden und der nächste Geburtstag – werden relativ zu diesem Referenzpunkt und nicht zum heutigen Tag berechnet.