Struct TimeContext 

pub struct TimeContext { /* private fields */ }

Explicit, immutable context for conversions that need one.

A TimeContext snapshots the active time-data bundle at construction time and selects which parts of that snapshot back context-required conversions. The default constructor TimeContext::new uses the monthly ΔT series from the captured bundle, matching the behaviour of previous versions; TimeContext::with_builtin_eop selects the daily IERS finals2000A.all series from that same snapshot for the highest-fidelity bundled UT1 path inside its coverage window.

ΔT / UT1 accuracy

Epoch range	Default context (monthly ΔT)	with_builtin_eop()
Pre-948 CE	±hundreds of s (Stephenson & Houlden quadratic)	same (outside EOP range)
948–1619	±15 s (Stephenson & Houlden)	same
1620–1973	±0.1–1 s (Meeus biennial table)	same
1973 – EOP start	~0.01 s (USNO monthly)	same
EOP observed range	< 15 ms from the bundled daily IERS-derived path over the compiled observed overlap	preferred highest-fidelity bundled UT1 path
EOP prediction range	< 0.2 s from the bundled short-range daily prediction over the compiled prediction overlap	preferred highest-fidelity bundled UT1 path
Beyond EOP	monthly ΔT only; prediction uncertainty grows	falls back to monthly ΔT

The builtin EOP is only consulted inside the captured bundle’s coverage; outside of that range the monthly ΔT path applies unchanged. Construct a fresh context after refreshing the active bundle if you want to use the updated runtime data.

Implementations

impl TimeContext

pub fn new() -> Self

Construct a default context backed by the monthly ΔT table.

This is the lightweight, always-available choice. It does not consult the daily EOP series even when the bundled data contains one.

pub fn with_builtin_eop() -> Self

Construct a context that prefers the compiled daily IERS finals2000A.all series for UT1 conversions when the epoch is within its coverage window.

Outside the bundled EOP coverage, this falls back to the same monthly ΔT path used by TimeContext::new.

pub fn allow_pre_definition_utc(self) -> Self

Allow UTC conversions for dates before 1961-01-01.

By default, Time::<UTC>::try_from_chrono_with and related conversions return crate::ConversionError::UtcBeforeDefinition for any date before MJD 37 300 (1961-01-01), because UTC was not an international standard before that date and the back-extrapolated offset is historically fabricated.

Calling this method on a context opts into the approximate continuation: the first official UTC-TAI segment is extrapolated backwards. Round-trips close, but the values are not standards-defined UTC.

Example

use tempoch_core::{TimeContext, Time, UTC};
use chrono::DateTime;

let dt = DateTime::from_timestamp(-631_152_000, 0).unwrap();
let ctx = TimeContext::new().allow_pre_definition_utc();
let utc = Time::<UTC>::try_from_chrono_with(dt, &ctx).unwrap();

pub fn eop_at(&self, mjd_utc: Day) -> Option<EopValues>

Interpolated EOP at mjd_utc, if this context has an EOP source and the MJD is in range.

This exposes the same interpolated values that context-backed scale conversions consult internally, so callers can inspect or reuse them without reimplementing the lookup path.

pub fn ut1_minus_utc(&self, mjd_utc: Day) -> Option<Second>

Interpolated UT1 - UTC from the context’s EOP source, if available.

Returns None when this context is monthly-ΔT-only or when the epoch is outside the captured EOP coverage window.

Trait Implementations

impl Clone for TimeContext

fn clone(&self) -> TimeContext

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for TimeContext

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for TimeContext

fn default() -> Self

Returns the “default value” for a type.