thndrs_lib/core/utils/
datetime.rs

1/// Get the current time as an ISO 8601 UTC string.
2///
3/// Format: `YYYY-MM-DDTHH:MM:SSZ`.
4pub fn now_iso8601() -> String {
5    let secs = std::time::SystemTime::now()
6        .duration_since(std::time::UNIX_EPOCH)
7        .unwrap_or_default()
8        .as_secs();
9
10    let days = secs / 86_400;
11    let remainder = secs % 86_400;
12    let hour = remainder / 3600;
13    let minute = (remainder % 3600) / 60;
14    let second = remainder % 60;
15
16    format!("{}T{hour:02}:{minute:02}:{second:02}Z", date_from_days(days))
17}
18
19/// Format a Unix timestamp as an ISO 8601 UTC string.
20pub fn from_unix_seconds(secs: u64) -> String {
21    let days = secs / 86_400;
22    let remainder = secs % 86_400;
23    let hour = remainder / 3600;
24    let minute = (remainder % 3600) / 60;
25    let second = remainder % 60;
26    format!("{}T{hour:02}:{minute:02}:{second:02}Z", date_from_days(days))
27}
28
29/// Convert days since Unix epoch to a YYYY-MM-DD string.
30///
31/// Uses the Howard Hinnant algorithm for date calculation.
32pub fn date_from_days(days: u64) -> String {
33    let z = days as i64 + 719_468;
34    let era = if z >= 0 { z } else { z - 146_096 } / 146_097;
35    let doe = z - era * 146_097;
36    let yoe = (doe - doe / 1_460 + doe / 36_524 - doe / 146_096) / 365;
37    let y = yoe + era * 400;
38    let doy = doe - (365 * yoe + yoe / 4 - yoe / 100);
39    let mp = (5 * doy + 2) / 153;
40    let d = doy - (153 * mp + 2) / 5 + 1;
41    let m = if mp < 10 { mp + 3 } else { mp - 9 };
42    let y = if m <= 2 { y + 1 } else { y };
43    format!("{y:04}-{m:02}-{d:02}")
44}
45
46/// Get the current date rounded to the day (YYYY-MM-DD) for cache stability.
47///
48/// The exact timestamp stays in session JSONL metadata when needed for audit.
49pub fn rounded_date() -> String {
50    let now = std::time::SystemTime::now()
51        .duration_since(std::time::UNIX_EPOCH)
52        .unwrap_or_default()
53        .as_secs();
54
55    date_from_days(now / 86_400)
56}
57
58#[cfg(test)]
59mod tests {
60    use super::*;
61
62    #[test]
63    fn date_from_days_known_values() {
64        assert_eq!(date_from_days(0), "1970-01-01");
65        let d = date_from_days(20_745);
66        assert!(d.starts_with("2026"), "day 20745 should be in 2026, got {d}");
67    }
68}
thndrs_lib/core/utils/datetime.rs

thndrs_lib/core/utils/
datetime.rs
