Emacs Org-Mode, along with its org-capture mode and the ability to clock in/out, is a perfect tool to implement this, btw.

I love org-mode but I don't use Emacs. Here is (almost complete) vim equivalent: https://github.com/jceb/vim-orgmode

With vim-orgmode I can quickly edit stuff in familiar editor.

I have tried various other formats, including taskpaper and various to-do lists but org-mode stands out by far.

Another great vim option is vimwiki: https://github.com/vimwiki/vimwiki

At a glance it supports all of the features provided by vim-orgmode, but it will probably never be as fully featured as emacs' orgmode