One final achievement of Aryabhata was that he came up with an extremely accurate number for a sidereal year. A sidereal year is the period of time it takes for the earth to fully orbit the sun. His estimate for the sidereal year was 365 day 6 hour 12 minutes 30 seconds. This was 3 minutes 20 seconds longer than the true value of 365 days 6 hours 9 minutes 10 seconds! He was extremely accurate for someone alive so long ago. The very close estimate for the sidereal year was a significant because people back then and now can know their age correctly, as well as the year. In earlier years, many cultures would tell time by the season. Although it worked the system was not very accurate. Another way this was useful is that people now and then could lease or rent something and know exactly when to return it. Because of this, Aryabhata should also win a Nobel Prize for his estimate for a sidereal year which changed the use of time for many cultures.