Shell variable PROMPT_COMMAND not working as intended?
Your date call got evaluated when you set PROMPT_COMMAND so it is forever stuck at the  time that you ran:

export PROMPT_COMMAND="echo -n ┏━━━[$(date +%H:%M)]"


Try defining a function instead and assigning that to PROMPT_COMMAND:

function prompt_command() {
    PS1="┏━━━[$(date +%H:%M)]━━[\t]━━━┓\n\$ "
}
export PROMPT_COMMAND=prompt_command


You can also use \@ for the current time in 12-hour AM/PM format in your prompt. So:

function prompt_command() {
    PS1="┏━━━[\@]━━[\t]━━━┓\n\$ "
}
export PROMPT_COMMAND=prompt_command


Would give you:

┏━━━[06:17 PM]━━[18:17:57]━━━┓
$


And while we're talking bash customizations let me put in a plug for the excellent bash-it project -- it's a bash equivalent to oh-my-zsh and it comes with a bunch of helper functions for theme creation. You might find it makes this sort of thing a little easier.