Comment by Galactic Navy Officer on Innocent

@Innocent Part of the reason for that would be the life he's living. Have you ever had to check the calendar to see what day it is, because a whole bunch of days have been very similar? He doesn't have a calendar, and most of the days he's been living are very much the same. While time can be seen as the seasons pass and animals are born and die and the moon changes, it all blends together after a while. 

He was marking off the days for a while, but he lost his initial tally when the troll damaged his tree home. He could've tried to remember how many he had, but it would have been difficult. Add in getting sick from his dragon curse (before he got that removed) and any other illness, and not being in a state to mark the days, and after a while, he probably only marked the turning of the year.

The issue of time passing, to those born without a mind that can handle immortality, is probably why a lot of wizards and others who figure out how to live long live in places where days easily blend together and hate being disturbed. (Cultivation doesn't factor here, because part of cultivating is developing the mind that can handle immortality.)