31 lines
1.2 KiB
Rust
31 lines
1.2 KiB
Rust
//! Conversions between Modified Julian Date and Julian Date.
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//!
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//! A Julian Date counts days from noon on 4713-01-01 in the proleptic
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//! Julian calendar. A Modified Julian Date counts days from midnight on
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//! 1858-11-17. The two therefore differ by a fixed number of days, and the
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//! half day offset accounts for the different times of day at which each
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//! scale starts a day.
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//!
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//! The offset is exact, so these conversions introduce no rounding beyond
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//! the representation of the input.
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/// The number of days between the start of the Julian Date scale and the
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/// start of the Modified Julian Date scale.
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///
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/// 儒略日标度起点与修正儒略日标度起点之间的天数。
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pub const JULIAN_DATE_OFFSET: f64 = 2_400_000.5;
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/// Converts a Julian Date to a Modified Julian Date.
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///
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/// 把儒略日（Julian Date）转换为修正儒略日（Modified Julian Date）。
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pub const fn mjd_from_julian_date(julian_date: f64) -> f64 {
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julian_date - JULIAN_DATE_OFFSET
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}
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/// Converts a Modified Julian Date to a Julian Date.
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///
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/// 把修正儒略日（Modified Julian Date）转换为儒略日（Julian Date）。
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pub const fn julian_date_from_mjd(mjd: f64) -> f64 {
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mjd + JULIAN_DATE_OFFSET
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}
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