In stories and folklore, the Witching Hour is usually the wee hours of the morning, such as Midnight. But for those of us with children, we all know that this a misinterpretation. The real Witching Hour is about 4-6 pm.
Between 4 and 6pm, no matter where we are, no matter what the day has held, my children go berserk. They're tired. They're hungry (even if they just had a snack!). They are wound up and ready to tear each other apart, while vying for undivided parental attention.
In the car? Choruses of repeated soundified cacophony, bounced back and forth, or punctuated with "DHO-WY!!!DHO-WY!!! BE QUIET! I NEED QUIET!!!!"
In the house? Stampedes of elephants rampage through the house, chasing two terrified cats, while singing "Blue's Clues" or the daily Favorite Ditty at the top of their lungs. Sometimes trucks are pushed by said elephants, exponentially increasing the noise.
In the yard? Sand is flung willy-nilly to squeals of protest and sandy bodies dashing past the parental guard into the house... where the child promptly turns into a very sandy elephant.
In the store? I avoid the store during the Witching Hour at all costs. We'll survive a single night without milk, bread, and toilet paper instead.
Any relief from the Witching Hour is infamously temporary. Nothing will eradicate it completely from a day. A method that provides relief today will not work for weeks to come. There is nothing to be done but batten down the sanity hatches and hold on tight... and enjoy the roller-coaster ride.