How time changes one (3)

I believe the answer is:

eon

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'how time' is the definition.
'eon' can be an answer for 'time' (I've seen this before). I am not sure about the 'how' bit.

'changes one' is the wordplay.
'changes' indicates an anagram.
'one' anagrammed gives 'EON'.

Can you help me to learn more?

(Other definitions for eon that I've seen before include "In time, long division" , "plenty of time" , "Huge time period" , "Vast age; eternity" , "Long period of time" .)

I've seen this clue in the Evening Standard.

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