We'd be Better Off with 9-bit Bytes
A number of 70s computing systems had nine-bit bytes, most prominently the PDP-10, but today1 [ 1 Apparently, it was the System/360 that really set the standard here.] all systems use 8-bit bytes and that now seems natural.2 [ 2 Though you still see RFCs use "octet", and the C standard has a CHAR_BITS macro, to handle the possibility of a different-sized byte.] As a power of two, eight is definitely nicer. But I think a series of historical coincidences would actually go our way with 9-bit bytes.
IPv4: Everyone knows the story: IPv4 had 32-bit addresses, so about 4 billion total.3 [ 3 Less due to various reserved subnets.] That's not enough in a world with 8 billion humans, and that's lead to NATs, more active network middleware, and the impossibly glacial pace of IPv6 roll-out. It's 2025 and Github—Github!—doesn't support IPv6. But in a world with 9-bit bytes IPv4 would have had 36-bit addresses, about 64 billion total. That would still be enough right now, and even with continuing growth in India and Africa it would probably be enough for about a decade more.4 [ 4 In our timeline, exhaustion hit in 2011, when demand was doubling every five years. 16× more addresses gets us to 2031 projecting linearly, and probably a little later with growth slowing.] When exhaustion does set in, it would plausibly at a time where there's not a lot of growth left in penetration, population, or devices, and mild market mechanisms instead of NATs would be the solution.
UNIX time: In our timeline, 32-bit UNIX timestamps run out in 2038, so again all software has to painfully transition to larger, 64-bit structures. Equivalent 36-bit timestamps last until 3058, so no hurry. Negative timestamps would represent any time since 882, so could cover the founding of Kievan Rus', the death of Alfred the Great, the collapse of the Classic Maya,5 [ 5 The people stuck around, but they stopped building cool cities.] and the movement of Magyar tribes into the Carpathian basin.
