The Microwave Challenge
JavaScript (ES6), 345 342 bytes

Saved 2 bytes thanks to @StephenLeppik

n=&gt;[...'lmnopqsuvwxyz{}~'].reduce((s,c)=&gt;(x=s.split(c)).join(x.pop()),` p{{yyvu{ xvs${(n&amp;&amp;n&lt;60?n+'':(k=n||new Date/6e4|0,k/60%(n?k:12)|0||(n?0:12))+':'+('0'+k%60).slice(-2)).padEnd(9)}xoup__uuxx{~zzn1s2s3wn4s5s6wn7s8s9wuuq 0sStartmy_~ { oxp__zxllx{|x
|p{_|{y_|qox}}}uzs}uuuuu {yyy__z|u y___s|wm|y~zzv
|}}}}xu  sx q~|p{{{ox
znzq m qy|ylx}|xv`)


Test cases



let f =

n=&gt;[...'lmnopqsuvwxyz{}~'].reduce((s,c)=&gt;(x=s.split(c)).join(x.pop()),` p{{yyvu{ xvs${(n&amp;&amp;n&lt;60?n+'':(k=n||new Date/6e4|0,k/60%(n?k:12)|0||(n?0:12))+':'+('0'+k%60).slice(-2)).padEnd(9)}xoup__uuxx{~zzn1s2s3wn4s5s6wn7s8s9wuuq 0sStartmy_~ { oxp__zxllx{|x
|p{_|{y_|qox}}}uzs}uuuuu {yyy__z|u y___s|wm|y~zzv
|}}}}xu  sx q~|p{{{ox
znzq m qy|ylx}|xv`)

O.innerText = [100, 59, 60, 120, 59999999, 1, 0].map(f).join('\n');
&lt;pre id=O&gt;&lt;/pre&gt;