The time during the wee hours of the morning beginning at the first sign of light and ending as soon as the sun breaks the horizon. In relation to staying up all night, as this is the time in which most people realize they are looking sketchy and sleep deprived. Nothing fit for society comes from this time in circumstance. You have had your fun now go to bed.
"Thank God I got home before Sketch O' Clock, my neighbors might start judging me..."

"I went to this awesome party last week! We kept it raging way past Sketch O' Clock!"
by Hysterika Zahmer March 26, 2013
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Texting the opposite gender past 12:00 am.
Texting the opposite gender, especially people you are interested in/they are interested into you, past 12:00 am
Texting the opposite gender, especially flirtatious people/people who will give you that type of attention, past 12:00 am.

usually texting/talking to the opposite gender past 12:00 am gets sketchy and emotional - therefore, becoming sketch-o-clock.
"OMG brad texted me!!!" "Giirrrllll he texted you at 12:00 am, it's sketch-o-clock, he wants something"
by doubleC^2 August 4, 2020
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