stay up until

stay up until (some hour)

To remain awake until some time, especially when it is past one's usual or required bedtime. I had to stay up until nearly 1 AM last night doing my taxes because I left them until the last minute again. We let Johnny stay up until midnight last night so he could do the New Year's Eve countdown with us.
See also: stay, until, up
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

stay up until

a particular time to remain awake and out of bed until a particular time. I stayed up until long past midnight last night. Do you think Susie should stay up until midnight?
See also: stay, until, up
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.
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