Definition.com
4 a.m. is distinguished from 5:00 AM in that 4am is late as fuck and 5am is early as hell.
Definition.com
4 a.m. is where you just stare at the clock and try to determine if it's late or early.
Definition.com
4 a.m. is a time that feels totally different when you have to wake up at 4am versus when you been up all night past 4am.
See also
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