Regarding the `timer` script, it appears to block the shell. A way to avoid this would be to spawn a subshell for the sleep command like this: `( sleep "$1" && notify ... ) &`
inoremap <Leader>date <C-r>=strftime("%a %B %e, %Y %H:%M:%S %p")<CR>
nnoremap <Leader>date :put=strftime("%a %B %e, %Y %H:%M:%S %p")<CR>
I am also not sure if an `<esc>` is really necessary at the end of your normal mode map.