TimeDelta

class astropy.time.TimeDelta(val, val2=None, format=None, scale=None, copy=False)

Bases: astropy.time.Time

Represent the time difference between two times.

A TimeDelta object is initialized with one or more times in the val argument. The input times in val must conform to the specified format. The optional val2 time input should be supplied only for numeric input formats (e.g. JD) where very high precision (better than 64-bit precision) is required.

The allowed values for format can be listed with:

>>> sorted(TimeDelta.FORMATS)
['jd', 'sec']

Note that for time differences, the scale can be among three groups: geocentric (‘tai’, ‘tt’, ‘tcg’), barycentric (‘tcb’, ‘tdb’), and rotational (‘ut1’). Within each of these, the scales for time differences are the same. Conversion between geocentric and barycentric is possible, as there is only a scale factor change, but one cannot convert to or from ‘ut1’, as this requires knowledge of the actual times, not just their difference. For a similar reason, ‘utc’ is not a valid scale for a time difference: a UTC day is not always 86400 seconds.

Parameters:

val : numpy ndarray, list, str, number, or TimeDelta object

Data to initialize table.

val2 : numpy ndarray, list, str, or number; optional

Data to initialize table.

format : str, optional

Format of input value(s)

scale : str, optional

Time scale of input value(s), must be one of the following values: (‘tdb’, ‘tt’, ‘ut1’, ‘tcg’, ‘tcb’, ‘tai’). If not given (or None), the scale is arbitrary; when added or subtracted from a Time instance, it will be used without conversion.

copy : bool, optional

Make a copy of the input values

Attributes Summary

FORMATS	Dict of time delta formats.
SCALES	List of time delta scales.

Methods Summary

replicate(*args, **kwargs)
to(*args, **kwargs)

Attributes Documentation

FORMATS = {u'jd': <class 'astropy.time.core.TimeDeltaJD'>, u'sec': <class 'astropy.time.core.TimeDeltaSec'>}

Dict of time delta formats.

SCALES = [u'tdb', u'tt', u'ut1', u'tcg', u'tcb', u'tai']

List of time delta scales.

Methods Documentation

replicate(*args, **kwargs)

to(*args, **kwargs)