However, the problem was n't completely solved by the Julian calendar, because a tropical year is n't 365.25 days long; it's 365.24219 days long. You still have a calendar drift problem, it just takes many centuries to become noticeable. And so, in 1582, Pope Gregory XIII instituted the Gregorian calendar, which was largely the same as the Julian Calendar, with one more trick added for leap years: even Century years (those ending with the digits 00) are only leap years if they are divisible by 400. So, the years 1700, 1800, and 1900 were not leap years (though they would have been under the Julian Calendar), whereas the year 2000 was a leap year. This change makes the average length of a year 365.2425 days. So, there is still a tiny calendar drift, but it amounts to an error of only 3 days in 10,000 years. The Gregorian calendar is still used as a standard calendar throughout most of the world.
Porén, o problema non ficou resolvido completamente co calendario xuliano porque un ano tropical non ten 365, 25 días, senón 365, 24219. Ainda fica un problema de deriva do calendario. Simplemente, lévalle varios séculos facerse visíbel. Por iso, en 1582 o papa Gregorio XIII instituíu o calendario gregoriano, que era fundamentalmente o mesmo que o xuliano cunha trampiña engadida aos anos bisextos: os anos do século pares (os que rematan nos díxitos 00) só son anos bisextos se xon divisíbeis por 400. Por isto, os anos 1700, 1800 e 1900 non foron anos bisextos (ainda que si o terían sido co calendario xuliano), mentres que o ano 200 si foi un ano bisexto. Esta alteración fai que a lonxitude media dun ano teña 365, 2425 días. Polo tanto, aínda hai unha pequena deriva, mais supón un erro de só tres días en 10. 000 anos. O calendario gregoriano utilízase ainda como calendario normal na maior parte do mundo.