Find specific day / time in previous week - rust

Question

I am using Rust with the Chrono library, and need to find the DateTime for the previous Tuesday at 6 PM UTC.
I have the following code, which seems to be working, but seems more complicated than it should be.
use chrono::{DateTime, Utc, Duration, Datelike};
use chrono::prelude::*;
fn main() {
let now: DateTime<Utc> = Utc::now();
let n_date = Utc::now().date();
let dt = Utc.ymd(n_date.year(), n_date.month(), n_date.day()).and_hms(18, 0, 0);
let current_day = now.weekday().number_from_monday();
let target_dt = if current_day == 2 {
if dt > now {
dt
} else {
dt - Duration::days(7)
}
}
else if current_day > 2 {
dt - Duration::days((current_day - 2) as i64)
} else {
dt - Duration::days(6)
};
println!("{:?}", target_dt);
}
Is there more efficient / better way to find a specific DateTime in the previous week? (In this case, the previous Tuesday at 18:00 UTC). Looking at some other languages, there are one line solutions, and I feel like I must be missing something obvious.
Based on the feedback below, here is the updated code:
let now: DateTime<Utc> = Utc::now();
//use this to test specific dates / times
//let now : DateTime<Utc> = Utc.ymd(2020, 11, 24).and_hms(18, 0, 1);
let n_date = now.date();
//let n_date = Utc.ymd(2020, 11, 24).and_hms(17, 0, 0).date();
let dt = Utc.ymd(n_date.year(), n_date.month(), n_date.day()).and_hms(18, 0, 0);
let w_day = n_date.weekday();
let target_dt = if w_day == Weekday::Tue {
if now > dt {
dt
} else {
dt - Duration::days(7)
}
} else {
let c:i64 = ((w_day.num_days_from_sunday() + 4) % 7 + 1) as i64;
dt - Duration::days(c)
};
println!("{:?}", target_dt);
ok. After thinking about this more, I figured out a more straight forward way, that plays off the fact that I can use a previous know reset data / time as a reference:
pub const WEEK_IN_SECONDS: i64 = 60 * 60 * 24 * 7;
pub fn get_last_reset() -> DateTime<Utc> {
//get a hardcoded past reset date / time
let past_reset : DateTime<Utc> = Utc.ymd(2020, 11, 10).and_hms(18, 0, 0);
let now: DateTime<Utc> = Utc::now();
//get total seconds between now and the past reset
//take the mod of that divided by a week in seconds
//subtract that amount from current date / time to find previous reset
now - Duration::seconds((now - past_reset).num_seconds() % WEEK_IN_SECONDS)
}

Answer 1

By shamelessly stealing ideas of both #MaxV and #Simson you can do the following: Playground
Fixed it to cover time below or above 18 hours on Tuesday
use chrono::{Utc, Duration, NaiveTime};
use chrono::prelude::*;
fn main() {
let now: DateTime<Utc> = Utc.ymd(2020, 11, 25).and_hms(17, 0, 0);
let now_date = now.date();
let current_day = now_date.weekday().number_from_monday() as i64;
let tuesday_correction = if current_day == 2 && now.time() < NaiveTime::from_hms(18, 0, 0) {7} else {0};
let days_to_tuesday = Duration::days((7 + current_day - 2) % 7 + tuesday_correction);
let target_date = (now_date - days_to_tuesday).and_hms(18, 0, 0);
println!("{:?}", target_date);
}

Answer 2

There is my solution for Tuesday 18:00: playground
use chrono::{Utc, Duration, Datelike, Date};
fn main() {
let now: Date<Utc> = Utc::now().date();
let days_since_previous_tue = match now.weekday().number_from_monday() {
/*Mon*/ 1 => 6,
/*Tue*/ 2 => 7,
/*Wed*/ 3 => 1,
/*Thu*/ 4 => 2,
/*Fri*/ 5 => 3,
/*Sat*/ 6 => 4,
/*Sun*/ 7 => 5,
_ => panic!("Incorrect number_from_monday"),
};
let target = (now - Duration::days(days_since_previous_tue)).and_hms(18, 0, 0);
println!("Target date:{:?}", target);
}
It's not generic enough to process any possible day but I believe it shows the idea. Please let me know if you're interested in generic solution for any day/time.