Astro:...DeltaT(3pm)

💫 Astro::Montenbruck::Time::DeltaT 💫

ok so this is the Astro::Montenbruck::Time::DeltaT page from the User Contributed Perl Documentation, and bestie, it's literally just about the difference between UT and TDT. that's the whole vibe. let's get into it 🫶

🌸 NAME 🌸

Astro::Montenbruck::Time::DeltaT — the difference between UT and TDT. yes that's it, that's the name, no cap ✨

🎀 VERSION 🎀

Version 0.01 — baby's first version, we love a fresh release 💅

🦋 DESCRIPTION 🦋

okay so Delta-T is the difference between UT and TDT (Terrestrial Dynamic Time) — and fun little history fact, TDT used to be called Ephemeris time back in the last century, iconic rebrand honestly 👑

here's the tea: UT is not a uniform time scale. it gets occasionally adjusted because the Earth's rotation is a whole mess of irregularities (she wobbles, she's doing her best 😭). TDT, on the other hand, IS a uniform time scale, and you need it as an argument for mathematical theories of celestial movements. so like, one of these is reliable and one of these is UT. periodt.

the formulae used by the delta_t( $jd ) subroutine are based on the NASA Technical Publication "Five Millennium Canon of Solar Eclipses: -1999 to +3000". they're valid for any time during the interval 2000 B.C. to 3000 A.D. — yeah, five whole millennia, she ate 🔥

see the NASA Eclipse web site at <http://eclipse.gsfc.nasa.gov/SEcat5/deltatpoly.html"> for the source material 🌈

⭐ EXPORT ⭐

• delta_t( $jd ) — that's the one export, that's her, she's the main character 💖

💜 SUBROUTINES 💜

🌙 delta_t( $jd )

returns the approximate Delta-T in seconds for a given Julian Day. simple as that 🎯

and because the math needs to be said out loud:

Delta-T = ET - UT

for the historical range from 1620 to recent years, we interpolate from a table of observed values (real ones, we measured those, we're not just guessing 🙈). outside that range we use formulae from Astronomical Algorithms by J.Meeus, second edition — yes, Meeus, the legend, we stan 📚

🧚 Arguments

• $jd — a Standard Julian Date. that's the whole argument. she's straightforward 🍓

🏆 Returns

• Delta-T in seconds ⏱️

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ok that's the whole page!! no filler, no fluff, just time math and Earth being irregular 💀 stay slay, go compute some celestial movements bestie 💅✨

written with love in perl v5.42.2, dated 2026-02-15 — that's the source/version and the date, and this little sign-off is where the footer would've been 🎀