TimeJulianEpoch#

class astropy.time.TimeJulianEpoch(val1, val2, scale, precision, in_subfmt, out_subfmt, from_jd=False)[source]#

Bases: TimeEpochDate

Julian epoch year as decimal value(s) like 2000.0.

This format is based the Julian year which is exactly 365.25 days/year and a day is exactly 86400 SI seconds.

The Julian epoch year is defined so that 2000.0 is 12:00 TT on January 1, 2000. Using astropy this is expressed as:

>>> from astropy.time import Time
>>> import astropy.units as u
>>> j2000_epoch = Time("2000-01-01T12:00:00", scale="tt")
>>> print(j2000_epoch.jyear)
2000.0
>>> print((j2000_epoch + 365.25 * u.day).jyear)
2001.0

The Julian year is commonly used in astronomy for expressing the epoch of a source catalog or the time of an observation. The Julian epoch year is sometimes written as a string like “J2001.5” with a preceding “J”. You can initialize a Time object with such a string:

>>> print(Time("J2001.5").jyear)
2001.5

Attributes Summary

`epoch_to_jd`
`in_subfmt`
`jd1`
`jd2`
`jd_to_epoch`
`name`
`out_subfmt`
`precision`
`scale`	Time scale.
`subfmts`
`unit`
`value`	Return time representation from internal jd1 and jd2.

Methods Summary

`fill_value`(subfmt)	Return a value corresponding to J2000 (2000-01-01 12:00:00) in this format.
`set_jds`(val1, val2)	Set internal jd1 and jd2 from val1 and val2.
`to_value`(**kwargs)	Return time representation from internal jd1 and jd2.

Attributes Documentation

epoch_to_jd = 'epj2jd'#

in_subfmt#

jd1#

jd2#

jd_to_epoch = 'epj'#

name = 'jyear'#

out_subfmt#

precision#

scale#: Time scale.

subfmts = (('float', <class 'numpy.float64'>, None, <ufunc 'add'>), ('long', <class 'numpy.longdouble'>, <function longdouble_to_twoval>, <function twoval_to_longdouble>), ('decimal', <class 'numpy.object_'>, <numpy.vectorize object>, <numpy.vectorize object>), ('str', <class 'numpy.str_'>, <numpy.vectorize object>, <numpy.vectorize object>), ('bytes', <class 'numpy.bytes_'>, <numpy.vectorize object>, <numpy.vectorize object>))#

unit = 365.25#

value#

Methods Documentation

classmethod fill_value(subfmt)#

Return a value corresponding to J2000 (2000-01-01 12:00:00) in this format.

This is used as a fill value for masked arrays to ensure that any ERFA operations on the masked array will not fail due to the masked value.

set_jds(val1, val2)#: Set internal jd1 and jd2 from val1 and val2. Must be provided by derived classes.

to_value(**kwargs)#: Return time representation from internal jd1 and jd2. Subclasses that require parent or to adjust the jds should override this method.