Sorry my mistake, a Minecraft day is 15 minutes, so this would be about 3.6 Minecraft day cycles.
It took me roughly 13 seconds to fly to y=100 from y=0, so... it would take 130 seconds to fly to 1000 blocks and 130 times 25.052 is exactly 3,256.76 seconds to reach y=25,052 so we divide that by 60 is roughly 54 minutes So this record could easily be broken. Also other people in the comments are saying this would take 20-40 days to do... this is nonsense. But this a little more than 2 minecraft days. But still.