Not really sure that I'm yet fully persuaded but the following is the result of reading too many difficult books with long words...

It seems the suitability of God’s immutability
depends upon his timelessness (and that shows off my rhymelessness).
Neither present, past nor future tenses adequately give the sensus
of God unchanging and unbending, no beginning and no ending.

We deny all temporality, assert his immortality.
He has no ‘when,’ no ‘now,’ no ‘then,’
there’s no succession, no progression, no cessation, no duration.
For him all ‘nows’ are simultaneous, but that don’t mean he’s instantaneous.

More alive than you or I, he was not born and will not die;
our timeless God who does not change and cannot lie.