# What does "the past day" mean exactly?

Cited from an article on Khan Academy:

Jacob distributed a survey to his fellow students asking them how many hours they'd spent playing sports in the past day.

Does "the past day" mean yesterday or any arbitrary day in the past? Or does it have other meaning? Thank you in advance.

"The past day" can mean either yesterday or the previous 24 hours. The survey that went out to students was probably something like: How many hours did you spend playing sports yesterday? But the article is talking about the survey after it happened, so if the article used "yesterday" you would think it meant your (the reader's) yesterday. Instead they use "the past day" to indicate it was the survey-taker's yesterday, at the time they completed the survey.

As others have pointed out, there is ambiguity; the term might refer to the 24 hours immediately preceding the time when the survey-taker is answering the question, or it might refer to the most recent complete midnight-to-midnight 24-hour period. From the context of the article (a secondary source) it is not clear which is meant. Personally, if I were designing the survey I would use "yesterday."

The term "the past day" does not refer to any arbitrary day in the past, except in the sense that the day the survey was handed out may have been arbitrary. "A previous day" carries that sense of arbitrariness, which means it would not be good to use in a statistical survey (which is supposed to be a snapshot in time, and all survey-takers should be answering for the same time period).

• Not exactly the same. "Yesterday" would always mean "the 24 hours ending at midnight" while "the past day" might mean "in the last 24 hours". But otherwise correct. Apr 8, 2021 at 13:22
• It's the "the" that makes it the particular prior day; had they said a past day, then it could be any day. As in, "... playing sports in a past day". This would be equivalent to "any past day" or "any day in the past*. As written, "the" applies to "day", so it means a particular day. I can see how it's not obvious to those coming from languages that use articles very differently than English, so "exactly what it sounds like" really alludes to how idiomatic it may be to native English speakers.
– CCTO
Apr 8, 2021 at 13:57
• I think this answer isn't entirely correct and DJClayworth pointed it out. 'In the past day' alludes to the past 24 hours and not necessarily strictly the day before that started at 12am and ended at 11:59pm. It is possible the wrong phrase was used in the example sentence to get the time frame the author actually wanted. If they specifically wanted yesterday, saying 'the day before' would have been more clear on that. Apr 8, 2021 at 16:42
• I don't think "exactly what it sounds like" is very helpful here -- you might consider removing that phrase from the answer? I think it can come across as a bit hostile if the asker doesn't know. (There are cases where a question makes it clear that the asker sees some obvious interpretation, and is just double-checking it, but this question doesn't seem to be like that, since the asker considers "some arbitrary day in the past" one of the possibilities. You and I know that that is not what it sounds like to us, but is apparently something it could sound like to the asker.) Apr 8, 2021 at 22:33
• I second the above sentiments. ‘In the past day’ is, at least in all dialects of English where I’ve encountered the term, generally synonymous with ‘in the past 24 hours’. It’s important to remember that ‘day’ in English means either a 24-hour period of time, or a calendar day, and the use of a particular article does not disambiguate the definition. Apr 8, 2021 at 23:43

It could either be the equivalent of "yesterday" - or it could mean "the past 24 hours". The meaning could extend into the past no further than that.

This usage is vague. While I will agree that the most likely intended meaning is "the past 24 hours", I would never use this where communication was critical, or where miscommunication was likely.

• I read it and understood "the last 24 hours", "the previous day" would mean "yesterday" to me. It is vague enough to be either though. Apr 8, 2021 at 12:31
• If I was answering the question at 7pm and included activity from 5pm from the previous day, no one should be upset with me because the term is fairly imprecise. However, if I mention something from the morning of the day before, it might feel a little weird, because it was like a day and a half ago. Apr 8, 2021 at 16:56
• @Adam Starrh User phuzi's "Vague" is precisely the case. Although I tend to agree with you, I would also not use this where accurate communication of a timeframe was important, or where a misunderstanding might be likely. Apr 9, 2021 at 11:52

As an idiom, the past {timeperiod} is practically always used to mean "the period of time that began {timeperiod} ago and ending now." So, for me writing this right now at 2021-04-08T05:27:00Z:

• "the past day" = 2021-04-07T05:27:00Z to 2021-04-08T05:27:00Z
• "the past hour" = 2021-04-08T04:27:00Z to 2021-04-08T05:27:00Z
• "the past year" = 2020-04-08T05:27:00Z to 2021-04-08T05:27:00Z

For day in particular, "the past day" can also mean "yesterday", somewhat informally.

As @randomhead noted in his answer, the reason this language was used rather than just saying "yesterday" is because the time that the survey was published is not the same as the time the survey is filled out.

• Thanks @wizzwizz4 for the improvement. I hate timezones too :) Apr 9, 2021 at 20:13

There is no exact meaning. It's ambiguous.

Arguably it means the previous day. Meaning, the day that ended on the midnight immediately before the question was asked. Although, in that case, the better phrase to use would have been "the previous day".

Arguably it means the 24-hour period that ended when the question was asked.

I would lean towards the latter.

The main thing to understand here is that "the past X" means "the most recent X". This is different from "a past X" which would mean "an X at some point before now". So "the past day" always refers to "the most recent day".

It's hard to be more precise than that, because the word "day" is often used informally and ambiguously; it could mean:

• A period of precisely 24 hours, starting at midnight, and ending just before the following midnight.
• A period of 24 hours, ending at the moment you hear or read this sentence.
• A period of daylight, less than 24 hours.
• A period between waking up and going back to sleep, which could be less or more than 24 hours.

Sometimes, even the seemingly precise "24 hours" is used informally to mean "both day-time and night-time", to distinguish from "during the day" which means "the hours of daylight".

In the particular context given, it doesn't actually make much difference which of these definitions we pick. The survey is actually asking "how much of your time do you spend playing sport?", and asking about a particular day is just a way of getting the answer as a number.