I started the game at November 13., finished it at Nov. 15. So four days growing. BUT! I have to confess I changed for two times starting Uru the date of my operating system. It was astonishing! The tree was very tall now. It was only a try to test the growing algorithm. I never really believed that it may depend on the operating system date, but it seems so.
If I return to my relto now, sometimes I think it is even a bit taller than before, but can be an illusion.
Just a quick warning about changing your system date to make your tree grow. If you have any time licensed software installed you risk invalidating your license by changing the system date drastically. It may be detected as an attempt at license manipulation.