day one(redirected from Day 1)
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The first day or the beginning of something. Honestly, I've loved Frank since day one, long before we officially started dating. I'm sorry, but your assistant has annoyed me from day one. How can you stand her constant cheerfulness?
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
the very beginning; the very first day. (*Typically: from ~; since ~.) You haven't done anything right since day one! You're fired! She was unhappy with her new car from day one.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.
n. the first day. (Often with since.) You haven’t done anything right since day one! You’re fired!
McGraw-Hill's Dictionary of American Slang and Colloquial Expressions Copyright © 2006 by The McGraw-Hill Companies, Inc. All rights reserved.