Convert timestamp in seconds into datetime in UTC as Rust function

utc_date.rs

use std::fmt;

#[derive(Clone, Debug)]
pub struct DateTime {
  /// Seconds after the minute - [0, 59]
  pub sec: i32,
  /// Minutes after the hour - [0, 59]
  pub min: i32,
  /// Hours after midnight - [0, 23]
  pub hour: i32,
  /// Day of the month - [1, 31]
  pub day: i32,
  /// Months since January - [1, 12]
  pub month: i32,
  /// Years
  pub year: i32
}

impl DateTime {
  pub fn new() -> Self {
    Self {
      sec: 0,
      min: 0,
      hour: 0,
      day: 0,
      month: 0,
      year: 0
    }
  }

  pub fn date(&self) -> Date {
    Date { day: self.day, month: self.month, year: self.year }
  }
}

impl fmt::Display for DateTime {
  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
    write!(f, "{:04}-{:02}-{:02} {:02}:{:02}:{:02} UTC",
      self.year, self.month, self.day, self.hour, self.min, self.sec)
  }
}

#[derive(Clone, Debug)]
pub struct Date {
  /// Day of the month - [1, 31]
  pub day: i32,
  /// Months since January - [1, 12]
  pub month: i32,
  /// Years
  pub year: i32
}

impl Date {
  pub fn new() -> Self {
    Self {
      day: 0,
      month: 0,
      year: 0
    }
  }
}

impl fmt::Display for Date {
  fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
    write!(f, "{:04}-{:02}-{:02} UTC",
      self.year, self.month, self.day)
  }
}

// Convert epoch seconds into date time.
fn seconds_to_datetime(ts: i64, tm: &mut DateTime) {
  let leapyear = |year| -> bool {
    year % 4 == 0 && (year % 100 != 0 || year % 400 == 0)
  };

  static MONTHS: [[i64; 12]; 2] = [
    [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31],
    [31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
  ];

  let mut year = 1970;

  let dayclock = ts % 86400;
  let mut dayno = ts / 86400;

  tm.sec = (dayclock % 60) as i32;
  tm.min = ((dayclock % 3600) / 60) as i32;
  tm.hour = (dayclock / 3600) as i32;

  loop {
    let yearsize = if leapyear(year) { 366 } else { 365 };
    if dayno >= yearsize {
      dayno -= yearsize;
      year += 1;
    } else {
      break;
    }
  }
  tm.year = year as i32;

  let mut mon = 0;
  while dayno >= MONTHS[if leapyear(year) { 1 } else { 0 }][mon] {
    dayno -= MONTHS[if leapyear(year) { 1 } else { 0 }][mon];
    mon += 1;
  }
  tm.month = mon as i32 + 1;
  tm.day = dayno as i32 + 1;
}

// Usage
let seconds = 1262391174;
let mut tm = DateTime::new();
seconds_to_datetime(seconds, &mut tm);
println!("{}", tm.date());
println!("{}", tm);

God