I use Capture Templates in Org Mode for all sorts of things. Frequently, I want to capture something to a date tree, which automatically organizes entries by Year->Month->Day.

The usual way of doing this is to specify the target file as part of the capture template, like this…

("d" "Daybook" entry
(file+datetree "~/org/daybook.org")
"* %?\n%t")

What I also wanted to do was capture to a date tree in the buffer I’m already visiting. This meant that I couldn’t specify the file name ahead of time. I assumed doing this would require a bunch of fancy tricks (I’m not good at writing lisp), but it turned out to be easy. I simply replaced what would normally be a string containing the target file’s name with buffer-file-name, like this…

("l" "Current file log entry" entry
(file+datetree buffer-file-name)
"* %? \n%u")

Now, I can easily add an entry to a date tree in any file I’m working on.