This post is now obsolete. You can install tty-clock from the repository.

Screenshot Tty-clock is a small program that displays a digital clock.

To compile it on Termux you'll need to download the sources from GitHub.

git clone https://github.com/xorg62/tty-clock.git

You'll also need the ncurses-dev package.

apt install ncurses-dev

Sadly, compiling with make doesn't really work with this one, I managed to compile it with the following command.

gcc -Wall -Werror -Wextra -std=c99 -pedantic -Wno-unused-parameter -lncurses -o tty-clock ttyclock.c

You can then install it with make install.