Generate a UK numberplate
JavaScript (ES6), 121 bytes
Expects (month)(year). The day is ignored.

m=&gt;y=&gt;&quot;9512444&quot;.replace(/./g,n=&gt;(100+(y-(m&lt;3))%50+50*(m&lt;3|m&gt;8)+n)[n]||'ABCDEFGHKLMNOPRSVWYJTUXZ'[Math.random()*(28-n)|0])

Try it online!