by day

by day

During the day. Often used to refer to one's employment or other typical daytime activities, in contrast with what they are apt to do "by night." By day, he was an average office clerk, but by night he was a crime-fighting vigilante. She's a teacher by day and an actress at the local theater by night.
See also: by
Farlex Dictionary of Idioms.

by day

 and by night
during the day; during the night. (Often used in simultaneous clauses for contrast.) By day, Mary worked in an office; by night, she took classes. Dave slept by day and worked by night.
See also: by
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.
See also:
  • by night
  • just another day at the office
  • day off
  • from one day to the next
  • day or night
  • hands-on
  • from day to day
  • make a day of (doing something)
  • make a day of doing
  • make a day of it
References in periodicals archive
Based on the needs assessment conducted by ACA in the fall of 2003, several critical needs were expressed by day camp directors.
Beginning with the end day camp training by design
Clinical and radiologic deterioration progressed, and by day 7, mechanical ventilation was begun.
Possible central nervous system infection by SARS coronavirus
In this study, "reduction in plasma HIV-1 of less than 0.72 log by day 6 after initiation of therapy predicted poor long-term responses in more than 99% of the patients." For those with less than a 0.96 log reduction, the chance of poor response at 12 weeks was 95%.
Physicians might want to look at viral load decline by day six of certain new treatments -- in order to quickly change a clearly ineffective regimen.
Viral load: small change by sixth day of treatment can often predict poor response
When the daily fecal Pb excretion was averaged across treatment groups, it was apparent that the majority ([is greater than] 96%) of unabsorbed fecal [sup.206]Pb tracer was eliminated over treatment days 1 and 2 and declined substantially to near 0 by day 5 in these juvenile monkeys (Figure 1A).
Oral Succimer Decreases the Gastrointestinal Absorption of Lead in Juvenile Monkeys
When stocks fall, one strategy used by day traders is the "Lizard Reversal." Traders watch for a stock that is going down all day, but at the very end it closes up.
Life of a Day Trader