Wednesday of Holy Week - Spy Wednesday.

So today is known as Spy Wednesday, spy as in ambush. It’s the beginning of the betrayal by Judas Iscariot. It's also known as Holy Wednesday, Holy & Great Wednesday & Good Wednesday. Traditionally, Tenebrae, a service of extinguishing candles, begins on the evening of this day. 

And in some places today is called Ugly Wednesday, Soot-Sweeping Wednesday or Black Wednesday, because chimneys used to be swept on this day to be clean for Easter. 

And in Malta, Wednesday of Shadows. Traditionally, children went to the parish church and drummed on the chairs to make the sound of thunderstorms, as their version of the "strepitus" sound at Tenebrae Wednesday. 

In Scandinavia it's known as Dymmelonsdagen. In Scandinavia, a dymbil is a piece of wood. Historically, the metal clapper of the church bells were replaced by dymbils on Holy Wednesday, to make a duller sound.