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"""
================
Date tick labels
================
Matplotlib date plotting is done by converting date instances into
days since an epoch (by default 1970-01-01T00:00:00). The
:mod:`matplotlib.dates` module provides the converter functions `.date2num`
and `.num2date` that convert `datetime.datetime` and `numpy.datetime64`
objects to and from Matplotlib's internal representation. These data
types are registered with the unit conversion mechanism described in
:mod:`matplotlib.units`, so the conversion happens automatically for the user.
The registration process also sets the default tick ``locator`` and
``formatter`` for the axis to be `~.matplotlib.dates.AutoDateLocator` and
`~.matplotlib.dates.AutoDateFormatter`.
An alternative formatter is the `~.dates.ConciseDateFormatter`,
used in the second ``Axes`` below (see
:doc:`/gallery/ticks/date_concise_formatter`), which often removes the need to
rotate the tick labels. The last ``Axes`` formats the dates manually, using
`~.dates.DateFormatter` to format the dates using the format strings documented
at `datetime.date.strftime`.
"""
import matplotlib.pyplot as plt
import matplotlib.cbook as cbook
import matplotlib.dates as mdates
# Load a numpy record array from yahoo csv data with fields date, open, high,
# low, close, volume, adj_close from the mpl-data/sample_data directory. The
# record array stores the date as an np.datetime64 with a day unit ('D') in
# the date column.
data = cbook.get_sample_data('goog.npz')['price_data']
fig, axs = plt.subplots(3, 1, figsize=(6.4, 7), layout='constrained')
# common to all three:
for ax in axs:
ax.plot('date', 'adj_close', data=data)
# Major ticks every half year, minor ticks every month,
ax.xaxis.set_major_locator(mdates.MonthLocator(bymonth=(1, 7)))
ax.xaxis.set_minor_locator(mdates.MonthLocator())
ax.grid(True)
ax.set_ylabel(r'Price [\$]')
# different formats:
ax = axs[0]
ax.set_title('DefaultFormatter', loc='left', y=0.85, x=0.02, fontsize='medium')
ax = axs[1]
ax.set_title('ConciseFormatter', loc='left', y=0.85, x=0.02, fontsize='medium')
ax.xaxis.set_major_formatter(
mdates.ConciseDateFormatter(ax.xaxis.get_major_locator()))
ax = axs[2]
ax.set_title('Manual DateFormatter', loc='left', y=0.85, x=0.02,
fontsize='medium')
# Text in the x-axis will be displayed in 'YYYY-mm' format.
ax.xaxis.set_major_formatter(mdates.DateFormatter('%Y-%b'))
# Rotates and right-aligns the x labels so they don't crowd each other.
for label in ax.get_xticklabels(which='major'):
label.set(rotation=30, horizontalalignment='right')
plt.show()
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