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use crate::date::Date;
use std::time::{SystemTime, UNIX_EPOCH};
// Timestamp of 2016-03-01 00:00:00 in UTC.
const BASE: u64 = 1456790400;
const BASE_YEAR: u16 = 2016;
const BASE_MONTH: u8 = 3;
// Days between leap days.
const CYCLE: u64 = 365 * 4 + 1;
const DAYS_BY_MONTH: [u8; 12] = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31];
pub fn today() -> Date {
let default = Date {
year: 2019,
month: 1,
day: 1,
};
try_today().unwrap_or(default)
}
fn try_today() -> Option<Date> {
let now = SystemTime::now();
let since_epoch = now.duration_since(UNIX_EPOCH).ok()?;
let secs = since_epoch.as_secs();
let approx_days = secs.checked_sub(BASE)? / 60 / 60 / 24;
let cycle = approx_days / CYCLE;
let mut rem = approx_days % CYCLE;
let mut year = BASE_YEAR + cycle as u16 * 4;
let mut month = BASE_MONTH;
loop {
let days_in_month = DAYS_BY_MONTH[month as usize - 1];
if rem < days_in_month as u64 {
let day = rem as u8 + 1;
return Some(Date { year, month, day });
}
rem -= days_in_month as u64;
year += (month == 12) as u16;
month = month % 12 + 1;
}
}
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