Struct DeltaT 

pub struct DeltaT;

Utilities for estimating ΔT (Delta T) values.

ΔT represents the difference between Terrestrial Time (TT) and Universal Time (UT1). These estimates are based on Espenak and Meeus polynomial fits updated in 2014.

Implementations

impl DeltaT

pub fn estimate(decimal_year: f64) -> Result<f64>

Estimates ΔT for a given decimal year.

Based on polynomial fits from Espenak & Meeus, updated 2014. See: https://www.eclipsewise.com/help/deltatpoly2014.html

Arguments

• decimal_year - Year with fractional part (e.g., 2024.5 for mid-2024)

Returns

Estimated ΔT in seconds

Errors

Returns error for years outside the valid range (-500 to 3000 CE)

Example

let delta_t = DeltaT::estimate(2024.0).unwrap();
assert!(delta_t > 60.0 && delta_t < 80.0); // Reasonable range for 2024

pub fn estimate_from_date(year: i32, month: u32) -> Result<f64>

Estimates ΔT from year and month.

Calculates decimal year as: year + (month - 0.5) / 12

Arguments

• year - Year
• month - Month (1-12)

Returns

Estimated ΔT in seconds

Errors

Returns error if month is outside the range 1-12.

pub fn estimate_from_date_like<D: Datelike>(date: D) -> Result<f64>

Estimates ΔT from any date-like type.

Convenience method that extracts the year and month from any chrono type that implements Datelike (DateTime, NaiveDateTime, NaiveDate, etc.).

Arguments

• date - Any date-like type

Returns

Estimated ΔT in seconds

Errors

Returns error if the date components are invalid.

Example

// Works with DateTime
let datetime = "2024-06-21T12:00:00-07:00".parse::<DateTime<FixedOffset>>().unwrap();
let delta_t = DeltaT::estimate_from_date_like(datetime).unwrap();
assert!(delta_t > 60.0 && delta_t < 80.0);

// Also works with NaiveDate
let date = NaiveDate::from_ymd_opt(2024, 6, 21).unwrap();
let delta_t2 = DeltaT::estimate_from_date_like(date).unwrap();
assert_eq!(delta_t, delta_t2);