agnoster-timestamp-newline - Agnoster variant with timestamp and newline added.

agnoster-timestamp-newline-zsh-themes

Agnoster modified with timestamp segment and newline

Just copy the agnoster-timestamp-newline.zsh-theme to your ~/.oh-my-zsh/custom/themes/ folder.

Then set ZSH_THEME="agnoster-timestamp-newline" inside your .zshrc.

Here's the official docs on how to do that.