Here's one possible solution:

alias ca='cd $(find . -maxdepth 1 -type d -printf "%T@ %p\n" | sort -n | tail -1 | cut -d" " -f2-)'

However, it has the disadvantage of:

• Using the output directly from find without using something like print0, which results in directories with spaces in the name to not be handled correctly.
• Entering . if that is the last modified directory.

Here's one possible solution:

alias ca='cd $(find . -maxdepth 1 -type d -printf "%T@ %p\n" | sort -n | tail -1 | cut -d" " -f2-)'

But it has the following problems:

• Using the output directly from find without using something like print0, which results in directories with spaces in the name to not be handled correctly.
• Entering . if that is the last modified directory, instead of one of the directories within ..