In the Universe whatever is temporary and likely to be temporary, that can be changed, or is changeable, anything that is incomplete. We cannot keep it with us, after getting the same and the end of that is certain- is Illusion.
The process and mode which helps us to know Omnipresent & about the Omnipresent / Param Satya. That is complete, permanent, it cannot be changed, is unchangeable and cannot be destroyed, beyond illusions / Incomplete knowledge. Hence it remains unchangeable within and beyond the time - is Spirituality.