I know I've read this story at least twice. The first time was somewhere in the early 1980s (say, no later than 1984), but I strongly suspect it was already a few decades old at that point. I later accidentally ran across it in the mid-to-late 1990s. Both times, it was inside hardback anthologies which I had checked out from public libraries. (Possibly different copies of the same anthology; I can't remember what else was included in either volume.) English language; apparently set in a near-future version of the USA.
Here's the basic plot:
The story starts with a veteran novelist having a chat with an executive -- an editor in a book publishing house, I think. The novelist is under contract to deliver a new manuscript by a certain deadline, and I think he's already blown it. This is unusual for him, so the editor wants to know why.
They end up verbally reviewing the novelist's daily routine. (I gather he's a bachelor who lives alone in an apartment.) On working days (probably Monday-Friday), his alarm always wakes him up at the same time. He gets up, showers, fixes some breakfast, and then at a certain time (say, 8:30 to 9:00 AM) he does his morning exercises to keep fit. Then he sits down at his typewriter to get cracking on his novel . . . and he swears that he just doesn't know where the time goes! Sometimes it seems as if he's barely warming up . . . when suddenly his clock says it's time to stop for lunch or dinner. He is painfully aware that this sounds like a really pathetic excuse for his lack of productivity.
This is where the story veers away from what might be expected to happen in the real world. Instead of berating the writer or insisting he try harder to eliminate distractions during his working hours, the editor is surprisingly sympathetic, as if he honestly believes that the writer is telling the literal truth. The editor refers the writer to a man who provides a special service. The specialist carries some exotic equipment into the writer's apartment and takes some readings.
It turns out that someone was, in fact, stealing large chunks of the writer's time during business hours. I believe it is stated that our perception of time depends upon the presence of certain particles, and with "modern science" it is possible to add or subtract many of those particles so that a given person seems to experience, say, just five minutes of duration in a timeframe which an impartial observer with his stopwatch would clock at an hour. Or it can be done the other way around, if need be, to greatly increase the "amount of time" which a person experiences, so that he could squeeze an hour of work into a matter of minutes. Some crooks picked this bachelor writer as a soft target and have covertly stolen many, many hours' worth of time particles from him over the past several months (or however long it had been going on). Then they'd have a stockpile of "extra time" to sell on the black market.
Please note: There was also a legitimate, government-regulated service that would help you voluntarily sell some of your extra time, or you could buy some that another person had provided, but I got the impression that the writer had not previously been aware of this new industry (neither in its legitimate nor criminal variations), which is why the sympathetic editor was needed to diagnose what might really be happening. I presume that the criminals undercut the standard price from the legitimate service, which they could afford to do since they were not paying anything to the involuntary "time donors."
The thieves are apprehended by the forces of law and order, and the writer is notified that his now-retrieved "stolen time" is being held (by the legitimate service) in a new account in his name, and whenever he needs to add a few extra hours' worth of duration to his workday, he should just let them know. (I think a small percentage of his "stolen time" was kept by the legitimate service as their commission.)
At the end of the story, the writer is back in the editor's office for another session, but this time he is far more cheerful about it. He's been getting lots and lots of good work done at his typewriter, and after some experiments, he found that most of the time he doesn't even need to draw upon his account in order to add "extra hours" of working time to his day. The editor comments that he too usually feels the same way, although occasionally he arranges to have "a forty-hour day" (or something along those lines -- I could have the number wrong).
As you can see, I remember the plot pretty well, but I have no idea who wrote it. Nor do I recall the title. I have a vague idea that the second time I read that story (in the 1990s), I may have thought to myself: "This wasn't written by Isaac Asimov, but the writing style is similar to how he used to compose his own short stories, back in the Golden Age."
Does anyone think this sounds familiar?