Merge pull request #17990 from jklymak/auto-backport-of-pr-17983-on-v3.3.x

dstansby · web-flow · commit ac6aa6e2c9a5 · 2020-07-21T09:13:28.000+01:00
Manual backport of pr 17983 on v3.3.x
diff --git a/doc/api/api_changes_3.4/deprecations.rst b/doc/api/api_changes_3.4/deprecations.rst
@@ -1,2 +1,11 @@
 Deprecations
 ------------
+
+Reverted deprecation of `~.dates.num2epoch` and `~.dates.epoch2num`
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+These two functions were deprecated in 3.3.0, and did not return
+an accurate Matplotlib datenum relative to the new Matplotlib epoch
+handling (`~.dates.get_epoch` and :rc:`date.epoch`).  This version
+reverts the deprecation and fixes those functions to work with
+`~.dates.get_epoch`.
diff --git a/lib/matplotlib/dates.py b/lib/matplotlib/dates.py
@@ -1752,21 +1752,45 @@ def _get_interval(self):
         return self._interval
 
 
-@cbook.deprecated("3.3")
 def epoch2num(e):
     """
-    Convert an epoch or sequence of epochs to the new date format,
-    that is days since 0001.
+    Convert UNIX time to days since Matplotlib epoch.
+
+    Parameters
+    ----------
+    e : list of floats
+        Time in seconds since 1970-01-01.
+
+    Returns
+    -------
+    `numpy.array`
+        Time in days since Matplotlib epoch (see `~.dates.get_epoch()`).
     """
-    return EPOCH_OFFSET + np.asarray(e) / SEC_PER_DAY
+
+    dt = (np.datetime64('1970-01-01T00:00:00', 's') -
+          np.datetime64(get_epoch(), 's')).astype(float)
+
+    return (dt + np.asarray(e)) / SEC_PER_DAY
 
 
-@cbook.deprecated("3.3")
 def num2epoch(d):
     """
-    Convert days since 0001 to epoch.  *d* can be a number or sequence.
+    Convert days since Matplotlib epoch to UNIX time.
+
+    Parameters
+    ----------
+    d : list of floats
+        Time in days since Matplotlib epoch (see `~.dates.get_epoch()`).
+
+    Returns
+    -------
+    `numpy.array`
+        Time in seconds since 1970-01-01.
     """
-    return (np.asarray(d) - EPOCH_OFFSET) * SEC_PER_DAY
+    dt = (np.datetime64('1970-01-01T00:00:00', 's') -
+          np.datetime64(get_epoch(), 's')).astype(float)
+
+    return np.asarray(d) * SEC_PER_DAY - dt
 
 
 @cbook.deprecated("3.2")
diff --git a/lib/matplotlib/tests/test_dates.py b/lib/matplotlib/tests/test_dates.py
@@ -947,3 +947,15 @@ def test_change_epoch():
     np.testing.assert_allclose(
         mdates.date2num(np.datetime64('1970-01-01T12:00:00')),
         0.5)
+
+
+def test_epoch2num():
+    mdates._reset_epoch_test_example()
+    mdates.set_epoch('0000-12-31')
+    assert mdates.epoch2num(86400) == 719164.0
+    assert mdates.num2epoch(719165.0) == 86400 * 2
+    # set back to the default
+    mdates._reset_epoch_test_example()
+    mdates.set_epoch('1970-01-01T00:00:00')
+    assert mdates.epoch2num(86400) == 1.0
+    assert mdates.num2epoch(2.0) == 86400 * 2
