I have a character who is living through a very regular everyday routine for a longer time, let's say a couple of months. How do I describe this routine and give the impression of time passing by in an interesting way?
Multiple smaller scenes
You can have your main character play through a number of smaller scenes that present the repetitive nature of the routine. By breaking them up, you can introduce them one at a time, when they become relevant.
Have the character comment about it
The character might comment about it and give a quick run-down. By giving a quick overview, you can then have short scenes that expand elements and present them when the story needs it.
When something changes that routine, the MC - and reader - notice something is amiss.
"I have to get out of here! I can't take anymore of this. I'll run down, bump into Mr Rick and his dog. Then on the train for an hour with those over-perfumed ladies. Work for the unappreciation of my peers and sesame seeds. Then back for TV and a reheated can of ravioli. Let's see... five years now. Yeah, the glorious life!"
This creates a few sub-scenes: Rick and the dog, the train trip, work, watching TV, and the delicious can of ravioli.
Take things that happen every time with regularity, and make them not happen, so you can remember the last time they did not happen.
For example, consume things; I have a regular morning routine I've kept for 30 years, but it isn't precisely regular: I run out of coffee, or filters, or shampoo or toilet tissue, or the coffee pot dies. In thirty years, I've had two plumbing problems. You wake up on a few mornings and the electrical power is off. for all of these, you can remember the last time that happened.
You are also consuming time: For you in a few months, the season is changing, and the morning temperature changes, getting colder or getting warmer. Some days it is raining outside, or foggy, or snowing, or some days there are birds singing, the yellow roses are blooming. You see your neighbor's garden outside the kitchen window. If you start in Winter, close to Spring you see the garden start to thaw and green.
You may also be consuming people in this regularity:
When the garden changes, you see your neighbor Karen out there for the time in months, and she waves at you: Like she will every single morning, barring rain, until she once again shuts the garden down for the winter.
Your routine is on the bus, or you stop at a Starbucks. All the usual suspects are there. You may not know any of them, You may have a nodding recognition, but on various days one of the regulars is missing, or something is slightly different. The trenchcoat kid in the front left seat gets off at 23rd street instead of 31st. He's gotten off at 31st every day for two years, wtf trenchcoat kid? New job, or just an odd errand?
Heavy man is asleep in his seat this morning, that's different. Gray lady, two seats behind him, rises two minutes before they reach Heavy man's stop and shakes his shoulder, he wakes up, shakes his head awake, and then hurriedly packs his laptop and gets it back into that worn briefcase, ready to depart. She retakes her seat without a word.
The same things happen in the coffee shop; they messed something up and have no blueberry danish.
At the gym, the regulars change, quit, make progress.
The world is constantly changing, even if it is just the climate, and life happens. We get a cold, we consume things, we run out of things. We have unusual appointments to keep: A doctor or dentist appointment, dealing with the car mechanic or pest control, broken things to be fixed. Or you stayed up too late watching a game, or playing a game, or had a date.
No routine is completely stable and identical every single morning, every once in a while they get broken or interrupted.
More importantly, nearly all of us have some regular routines, so you can take advantage of other people's broken regularity to mark time in your own. Mike the coffee shop barista that has been there for a year is suddenly not, and the new guy screws up your order.
The bus driver changes, or there is some new weird guy on the bus. The gym manager changes, or somebody new shows up and has taken your treadmill.
You can allude to the routines; IRL they become part of muscle memory and you can do them without thinking about them, and while thinking of other things. It is the interruptions that are of note. If you just want to indicate the passage of time, these can be minor.
But you can make them part of the plot:
Karen starts to make coffee in the morning, and her tap water is off. A main must have broken. She resorts to using four bottles of her drinking water instead, which puts her behind ten minutes. She can't take a shower, so it will be a washrag affair with another six bottles. She needs to wash and rinse her hair. Which means she has to go buy more drinking water, off schedule, putting her in the grocery store on a Wednesday evening, instead of her usual Saturday morning. And there she sees --- one of her nodding acquaintances at the morning donut shop, an attractive young man that she knows owns exactly three good looking suits and is always in a hurry, and wears no ring. Now he is dressed in new jeans, a worn T-shirt with an engineering diagram of a Model T on it, and new sneakers. She makes an impulsive decision to get behind him in the checkout line.
"Hello, two lemon filled," she said.
The young man turns, surprised. "Ah. Apple Fritter. What finds you here?"
Karen gestures at her basket. "Water, my main was out this morning and I used all my drinking water." She offered a hand, "I'm Karen."
He took it, "Warren. Or lemon filled, as you see fit."
Ask yourself how you want the reader to feel about the routine. If it's monotonous, try being repetitive. List a bunch of boring tasks.
So once Bob returned from work, he hit the gym. He ate chicken and rice with some veg, then laundry and bed. Work, gym, chicken and rice, laundry, bed. Work, gym, laundry, bed.
Days bled into weeks. Weeks into months. Finally, just as summer was ending...
My biggest recommendation is: do not linger here. You can use a few paragraphs, sure, but do not have "Chapter 3: The Boring Month of Chores".
I do not care so much that they cleaned their reds before their whites, what I do care about is how the character is handling the tasks. Did they ruin a shirt because they stopped paying attention? Do they find comfort in the day-to-day after a hectic part of the story? Are they bored out of their mind?
Capture the whole of the time together, picking out whatever small highlights there are, because that is how it would feel. When you get into a routine, it all merges together into one long event.
- Focus on how the character feels during the time
- Give a sense of repetition and routine in your writing, don't just tell me about it.
- Do not linger on inaction, focus on highlights.
- Treat the entire period as one moment.
You would do this by mentioning the things he always has to do, preferrably in a dialogue or in a monologue from the character themselves if there are no others around.
Random Person 1: "Hey, wanna watch a movie together?"
MC: "Sorry, can't. I've got to go to the gym at eight. I do that every other day."
MC: "Damn, I need to get home to watch [Favourite TV Show]. It's starting in half an hour!"
You would have to weave this into the text, for example by portraying his colleagues at work or friends at a party. It's important to not just give a list of daily activities, if you are not specifically aiming for this sort of extreme rigorous routines.
After you've described everything over the course of maybe a chapter or two you would skip the rest. Repeating the same thing over and over again wouldn't be interesting to your reader and is not important for the story. Just skip it with "A few months of routine later" or something like that.
You can show the routine by going through a few days and shortening the different activities that do not play a big role for each day.
After running his 10km, which felt more like 20 after the exhausting conversation with Karen in the morning, he drank his cup of milk while preparing to watch the big game.
One example of actually writing out the routine is the beginning of American Psycho. Patrick Bateman narrates his morning routine. He does not see it as monotonous, it is a ritual. It's very precise and shows how he is attempting to tightly control his life and also prevent himself from aging. I mention it because the way the character describes his own routine is way to introduce a lot of important information about the character.
Another example is the beginning of "Your Appointment Will Be Yesterday" by Phillip K. Dick. In this case, the narrator is third person and we watch Niehls Lehrer, the main character, go through his morning routine. On the surface it's a mundane procession of breakfast, clothing, and personal hygiene, but everything is wrong - backwards. He doesn't shave, he glues 5:00 shadow to his face. He doesn't search for clean clothes, but for soiled ones that are wrinkled. We won't discuss the food situation here. It turns out that Lehrer is living in a reverse time field, and everything happens backwards. To arrive at work clean shaven with clean pressed clothes would be rude. Instead his hair grows inwards, retracts, and if he doesn't glue whiskers on, he won't have the clean shaven look by the end of the day. This time the routine establishes the setting.
Figure out why the reader has to know about this routine in the first place and start there. If the routine is not important to the story in some way, leave it out.
Honestly, you don't.
Everything that happens in your story must move the plot forward to justify its inclusion. It should give your characters personality (and strongly so - everyone has a daily routine, so showing a character going through their routine very rarely qualifies), introduce conflict, show characters making difficult decisions, foreshadow something that happens later, clarify an aspect of the setting that will become a plot point later on... Any scene that does not accomplish any of these goals will be tedious to read. There's no way to make a scene that doesn't advance the plot interesting. Your only viable options are to cut the scenes or tie them into the plot more strongly.
If nothing happens that advances your plot, your readers will be much happier with reading the words, "A few months later," at the top of the passage following the period of straightforward normality than having to slog through several pages that go nowhere.
If the fact that your character spends four months living an ordinary life are actually important to advancing your plot, you need to make sure you understand exactly why and then write the passage about those four months in a way that emphasizes those aspects. Don't write about the character's daily routine in general. Write only about the specific moments in or aspects of their routine that advance the plot.
For example, if your character spends several months on a daily routine because they're waiting for the love of their life to come back from war, emphasize how dealing with being away from their significant other affects their day-to-day life. If the character just got out of prison and is enjoying a pedestrian life for the first time in years, emphasize how the character takes pleasure in their newfound freedom.