/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
Now install coreutils (contains gdate) and gnu-sed (contains gsed)
brew install coreutils gnu-sed
Create a dir for lectl, download the latest version (0.11) and modify variables _date and _sed to point to gdate and gsed (installed with brew)
cd ~
mkdir lectl