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Deprecate Julian date-related functions and constant #24224

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Oct 20, 2022
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Deprecate Julian date-related functions and constant #24224

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5 changes: 5 additions & 0 deletions doc/api/next_api_changes/deprecations/24224-OG.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
``num2julian``, ``julian2num`` and ``JULIAN_OFFSET``
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

... of the `.dates` module are deprecated without replacements. These are
undocumented and not exported. If you rely on these, please make a local copy.
24 changes: 16 additions & 8 deletions lib/matplotlib/dates.py
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Expand Up @@ -202,6 +202,18 @@
UTC = datetime.timezone.utc


@_api.caching_module_getattr
class __getattr__:
JULIAN_OFFSET = _api.deprecated("3.7")(property(lambda self: 1721424.5))
# Julian date at 0000-12-31
# note that the Julian day epoch is achievable w/
# np.datetime64('-4713-11-24T12:00:00'); datetime64 is proleptic
# Gregorian and BC has a one-year offset. So
# np.datetime64('0000-12-31') - np.datetime64('-4713-11-24T12:00') =
# 1721424.5
# Ref: https://en.wikipedia.org/wiki/Julian_day


def _get_tzinfo(tz=None):
"""
Generate tzinfo from a string or return tzinfo. If None,
Expand All @@ -225,12 +237,6 @@ def _get_tzinfo(tz=None):
# Time-related constants.
EPOCH_OFFSET = float(datetime.datetime(1970, 1, 1).toordinal())
# EPOCH_OFFSET is not used by matplotlib
JULIAN_OFFSET = 1721424.5 # Julian date at 0000-12-31
# note that the Julian day epoch is achievable w/
# np.datetime64('-4713-11-24T12:00:00'); datetime64 is proleptic
# Gregorian and BC has a one-year offset. So
# np.datetime64('0000-12-31') - np.datetime64('-4713-11-24T12:00') = 1721424.5
# Ref: https://en.wikipedia.org/wiki/Julian_day
MICROSECONDLY = SECONDLY + 1
HOURS_PER_DAY = 24.
MIN_PER_HOUR = 60.
Expand Down Expand Up @@ -457,6 +463,7 @@ def date2num(d):
return d if iterable else d[0]


@_api.deprecated("3.7")
def julian2num(j):
"""
Convert a Julian date (or sequence) to a Matplotlib date (or sequence).
Expand All @@ -476,10 +483,11 @@ def julian2num(j):
ep0 = np.datetime64('0000-12-31T00:00:00', 'h').astype(float) / 24.
# Julian offset defined above is relative to 0000-12-31, but we need
# relative to our current epoch:
dt = JULIAN_OFFSET - ep0 + ep
dt = __getattr__("JULIAN_OFFSET") - ep0 + ep
return np.subtract(j, dt) # Handles both scalar & nonscalar j.


@_api.deprecated("3.7")
def num2julian(n):
"""
Convert a Matplotlib date (or sequence) to a Julian date (or sequence).
Expand All @@ -498,7 +506,7 @@ def num2julian(n):
ep0 = np.datetime64('0000-12-31T00:00:00', 'h').astype(float) / 24.
# Julian offset defined above is relative to 0000-12-31, but we need
# relative to our current epoch:
dt = JULIAN_OFFSET - ep0 + ep
dt = __getattr__("JULIAN_OFFSET") - ep0 + ep
return np.add(n, dt) # Handles both scalar & nonscalar j.


Expand Down
23 changes: 12 additions & 11 deletions lib/matplotlib/tests/test_dates.py
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Expand Up @@ -1241,17 +1241,18 @@ def test_change_interval_multiples():


def test_julian2num():
mdates._reset_epoch_test_example()
mdates.set_epoch('0000-12-31')
# 2440587.5 is julian date for 1970-01-01T00:00:00
# https://en.wikipedia.org/wiki/Julian_day
assert mdates.julian2num(2440588.5) == 719164.0
assert mdates.num2julian(719165.0) == 2440589.5
# set back to the default
mdates._reset_epoch_test_example()
mdates.set_epoch('1970-01-01T00:00:00')
assert mdates.julian2num(2440588.5) == 1.0
assert mdates.num2julian(2.0) == 2440589.5
with pytest.warns(_api.MatplotlibDeprecationWarning):
mdates._reset_epoch_test_example()
mdates.set_epoch('0000-12-31')
# 2440587.5 is julian date for 1970-01-01T00:00:00
# https://en.wikipedia.org/wiki/Julian_day
assert mdates.julian2num(2440588.5) == 719164.0
assert mdates.num2julian(719165.0) == 2440589.5
# set back to the default
mdates._reset_epoch_test_example()
mdates.set_epoch('1970-01-01T00:00:00')
assert mdates.julian2num(2440588.5) == 1.0
assert mdates.num2julian(2.0) == 2440589.5


def test_DateLocator():
Expand Down