A JavaScript Date object, a numeric UTC value expressed in J2000 days, or another AstroTime object.
The JavaScript Date object for the given date and time.
This Date corresponds to the numeric day value stored in the ut property.
Terrestrial Time in fractional days since the J2000 epoch. TT represents a continuously flowing ephemeris timescale independent of any variations of the Earth's rotation, and is adjusted from UT using a best-fit piecewise polynomial model devised by Espenak and Meeus.
Universal Time (UT1/UTC) in fractional days since the J2000 epoch. Universal Time represents time measured with respect to the Earth's rotation, tracking mean solar days. The Astronomy library approximates UT1 and UTC as being the same thing. This gives sufficient accuracy for the precision requirements of this project.
Returns a new AstroTime object adjusted by the floating point number of days.
Does NOT modify the original AstroTime object.
The floating point number of days by which to adjust the given date and time. Positive values adjust the date toward the future, and negative values adjust the date toward the past.
Formats an AstroTime object as an ISO 8601
date/time string in UTC, to millisecond resolution.
Example: 2018-08-17T17:22:04.050Z
StaticFromCreates an AstroTime value from a Terrestrial Time (TT) day value.
This function can be used in rare cases where a time must be based
on Terrestrial Time (TT) rather than Universal Time (UT).
Most developers will want to invoke new AstroTime(ut) with a universal time
instead of this function, because usually time is based on civil time adjusted
by leap seconds to match the Earth's rotation, rather than the uniformly
flowing TT used to calculate solar system dynamics. In rare cases
where the caller already knows TT, this function is provided to create
an AstroTime value that can be passed to Astronomy Engine functions.
The number of days since the J2000 epoch as expressed in Terrestrial Time.
An AstroTime object for the specified terrestrial time.
The date and time of an astronomical observation.
Objects of type
AstroTimeare used throughout the internals of the Astronomy library, and are included in certain return objects. Use the constructor or the MakeTime function to create anAstroTimeobject.