def test_change_epoch():
date = np.datetime64('2000-01-01')
# use private method to clear the epoch and allow it to be set...
mdates._reset_epoch_test_example()
mdates.get_epoch() # Set default.
with pytest.raises(RuntimeError):
# this should fail here because there is a sentinel on the epoch
# if the epoch has been used then it cannot be set.
mdates.set_epoch('0000-01-01')
mdates._reset_epoch_test_example()
mdates.set_epoch('1970-01-01')
dt = (date - np.datetime64('1970-01-01')).astype('datetime64[D]')
dt = dt.astype('int')
np.testing.assert_equal(mdates.date2num(date), float(dt))
mdates._reset_epoch_test_example()
mdates.set_epoch('0000-12-31')
np.testing.assert_equal(mdates.date2num(date), 730120.0)
mdates._reset_epoch_test_example()
mdates.set_epoch('1970-01-01T01:00:00')
np.testing.assert_allclose(mdates.date2num(date), dt - 1. / 24.)
mdates._reset_epoch_test_example()
mdates.set_epoch('1970-01-01T00:00:00')
np.testing.assert_allclose(
mdates.date2num(np.datetime64('1970-01-01T12:00:00')), 0.5)
mdates.set_epoch(old_epoch)
x = np.arange('2000-01-01T00:00:00.0',
'2000-01-01T00:00:00.000100',
dtype='datetime64[us]')
# simulate the plot being made using the old epoch
xold = np.array([mdates.num2date(mdates.date2num(d)) for d in x])
y = np.arange(0, len(x))
# resetting the Epoch so plots are comparable
_reset_epoch_for_tutorial() # Don't do this. Just for this tutorial.
mdates.set_epoch(new_epoch)
fig, ax = plt.subplots(constrained_layout=True)
ax.plot(xold, y)
ax.set_title('Epoch: ' + mdates.get_epoch())
plt.setp(ax.xaxis.get_majorticklabels(), rotation=40)
plt.show()
#############################################################################
# For dates plotted using the more recent epoch, the plot is smooth:
fig, ax = plt.subplots(constrained_layout=True)
ax.plot(x, y)
ax.set_title('Epoch: ' + mdates.get_epoch())
plt.setp(ax.xaxis.get_majorticklabels(), rotation=40)
plt.show()
_reset_epoch_for_tutorial() # Don't do this. Just for this tutorial.
#############################################################################