Enum Epoch 

pub enum Epoch {
    JulianPeriod,
    JulianCalendar,
    GregorianCalendar,
    Spreadsheet,
    J1900_0,
    Ntp,
    Unix,
    TimeStandard,
    Y1977,
    J1991_25,
    Y2k,
    J2000_0,
    J2100_0,
    J2200_0,
}

A reference for a well known Instant in time, used for offsetting events from.

Variants

JulianPeriod

The start of the Julian Period, which is 4713 BCE on Jan 1st Julian, 12:00:00.0 TT which is 4714 BCE on Nov 24 Gregorian, 12:00:00.0 TT JD 0 (by definition)

JulianCalendar

The start of the Julian Calendar period, which is January 1st, CE 1, Julian, 00:00:00.0 TT Specified in TT Note that this is exactly two days prior to the Gregorian Epoch.

Not to be confused with the Epoch::JulianPeriod which is much earlier. JD 1721423.5 (unverified, based on 2 day offset from Gregorian)

GregorianCalendar

The start of the Gregorian Calendar period, which is January 1st, CE 1, Gregorian, 00:00:00.0 TT JD 1721425.5

Spreadsheet

The Spreadsheet Epoch Which is December 30, 1899 CE gregorian, 00:00:00.0 UTC This is the point from which dates in a spreadsheet are counted as the (floating point) number of days since. JD 2415018.500476666666 // 32.184 [TAI-TT] + 9 [UTC-TAI]

J1900_0

The J1900.0 astronomical epoch, which is December 31, 1899 CE gregorian, 12:00:00.0 TT JD 2415020.0 (verified at https://www.astronomyclub.xyz/celestial-sphere-2/epochs-for-coordinate-systems.html)

Ntp

The NTP time base used in the IANA leap seconds file which is January 1st, 1900 CE gregorian, 00:00:00.0 UTC (seconds elapsed since 1900-01-01 00:00:00 UTC, except the leap seconds themselves) JD 2415020.500476666666 // 32.184 [TAI-TT] + 9 [UTC-TAI]

Unix

The UNIX Epoch, which is January 1st, 1970 CE gregorian, 00:00:00.0 UTC JD 2440587.500476666666 // 32.184 [TAI-TT] + 9 [UTC-TAI]

TimeStandard

The epoch where TT, TCB, and TCG all read the same. which is January 1st, 1977 CE gregorian, 00:00:00 TAI JD 2443144.5003725 (verified at https://en.wikipedia.org/wiki/International_Atomic_Time) This is 16 seconds different from this date in UTC, and another 32.184 [TAI-TT] from TT.

Y1977

A year I use for testing 1977-1-1 00:00:00 UTC

J1991_25

The J1991.25 astronomical epoch, which is April 2, 1991 CE gregorian, 13:30:00.0 TT JD 2448349.0625 (verified at https://www.astronomyclub.xyz/celestial-sphere-2/epochs-for-coordinate-systems.html)

Y2k

The Year 2000 which is January 1st, 2000 CE gregorian, 00:00:00.0 UTC JD 2451544.50074287037 // 32.184 [TAI-TT] + 32 [UTC-TAI]

J2000_0

The J2000.0 astronomical epoch, which is January 1, 2000 CE gregorian, 12:00:00.0 TT JD 2451545.0 (verified at https://www.astronomyclub.xyz/celestial-sphere-2/epochs-for-coordinate-systems.html) (verified at https://en.wikipedia.org/wiki/Epoch_(astronomy))

J2100_0

The J2100.0 astronomical epoch, which is January 1, 2100 CE gregorian, 12:00:00.0 TT JD 2488070.0 (verified at https://www.astronomyclub.xyz/celestial-sphere-2/epochs-for-coordinate-systems.html)

J2200_0

The J2200.0 astronomical epoch, which is January 2, 2200 CE gregorian, 12:00:00.0 TT JD 2524595.0 (verified at https://www.astronomyclub.xyz/celestial-sphere-2/epochs-for-coordinate-systems.html)

Implementations

impl Epoch

pub const fn as_instant(&self) -> Instant

Generate the Instant that this Epoch refers to