This riddle and its answer, from the Anglo-Saxon wisdom poem Solomon and Saturn II, appear at ll. 296-317 in Krapp and Dobbie’s numbering. Like the Raging Wulf riddle earlier in the same piece (read it with translation here), it is excellent poetry. Note the possibly deliberate irony of a man called Saturn (i.e. Cronos) asking a question about the ravages of time!
“Ac hwæt is ðæt wundor ðe geond ðas worold færeð,
styrnenga  gæð, staðolas beateð,
aweceð wopdropan, winneð oft hider?
Ne mæg hit steorra ne stan ne se steapa gimm,
wæter ne wildeor wihte beswican,
ac him on hand gæð heardes and hnesces,
micles [and] mætes; him to mose sceall
gegangan geara gehwelce grundbuendra,
ðria ðreoteno ðusendgerimes.”
“Yldo beoð on eorðan æghwæs cræftig;
mid hiðendre hildewræsne,
rumre racenteage, ræceð wide,
langre linan, lisseð  eall ðæt heo wile.
Beam heo abreoteð and bebriceð telgum,
astyreð standene  stefn on siðe,
afilleð hine on foldan  friteð æfter ðam
wildne fugol. Heo oferwigeð wulf, 
hio oferbideð stanas, heo oferstigeð style,
hio abiteð iren mid ome, deð usic swa.”
Note that my translation differs in a couple of places from others previously published, as detailed in the notes.
And what is the wonder which travels the world
Proceding inexorably, beating against strongholds,
it brings tears and often breaks through our defences?
Neither star nor stone, nor magnificent gem,
water nor wild beast can withstand it one bit.
But into its power go hard and soft,
great and small. It devours
annually many creatures that dwell on land,
fly through the air and swim in the water,
thirty-three thousand in number.
Old age is strong enough for anything on earth
with ravaging war-shackles,
copious chains reaching wide,
with its long line, it gathers everything it wants.
It destroys the tree and breaks it into small pieces
(the trunk in its plunge disturbs the rocky valley)
It fells to the ground and then devours
the wild bird. It outfights the wolf
it outwaits the stones, it outclimbs the stile
it gnaws iron with rust and treats us the same.
Notes re translation:
 styrnenga is a HL, but is likely to be real. It derives from styrne (‘stern’). There are plenty of other adverbs ending in -inga/-unga. It might just be an error for styrne gangeð, but the meaning would be the same.
 lisseð – an imaginary hapax legomenon. Not from the non-existent lissan/lissian, subdue, but from lesan, gather (normally spelled lisð). This impostor is found in B-T as ‘lissan’, in Clarke Hall as ‘lissian’. Anlezark continues to read ‘lissian’, showing that hapax legomena die hard.
 The standard emendation (Krapp & Dobbie, Anlazark) of the ms. astyreð stan dene (or standene – the gap between stan and dene is very small) to astyreð standendne is unnecessary and has caused confusion over the reading of the following line. Standendne is the pres. part. of stan, ‘stand’ and is read as modifying stefn and on siðe is assigned an adverbial meaning of ‘at last’. But the ms. has standene, which easily means rocky valley (stan + denu acc. sing.) and on siðe here means not ‘at last’ (which it can also mean) but ‘on its way’ (i.e. down). So the line means:
“the trunk in its plunge disturbs the rocky valley”
 afilleð hine on foldan is ambiguous, as it could refer either to the previously mentioned tree, or to the subsequently mentioned bird. With the emendation to standendne and assuming natural word-order, hine seemed to refer to the tree. But if the subject of the previous sentence is the tree, it is syntactically a wrench to move back to yldo as the subject with the previous subject (the tree) as the object. What is more, the sequence ‘he fells the tree to earth and then afterwards eats the wild bird’ is weak and clumsy, as the and æfter ðam is a nonsense connector. On the other hand, ‘it brings (him) down to earth and afterwards eats the wild bird’ is more natural and syntactically logical. The initial ambiguity is resolved by the delayed referent for hine, which is a nice poetic effect.
 Menner, following previous would-be mutilators, wanted to amend: ‘wildne fugol. Heo oferwigeð wulf’ ; to: ‘wulf heo oferwigeð, wildne fugol’ to restore the supposedly sacrosanct poetic structure of two alliterating syllables in the first half-line and one in the second. Don’t let the fact that then next line has exactly the same 1 + 2 structure stop us – hell, let’s write it backwards just for fun! Shame that this emendation for supposed poetic reasons would completely ruin the beautiful parallelism of:
Heo oferwigeð wulf, hio oferbideð stanas, heo oferstigeð style
Luckily this horror, while noted, was not adopted by either Krapp and Dobbie or Anlezark!