Datetime tutorial: Change symbol usde in first code example to fix failing under Windows (#3121)

Author: yvonnefroehlich

examples/tutorials/advanced/date_time_charts.py

@@ -29,8 +29,8 @@
 # data points stored in the list ``x``. Additionally, dates are passed into
 # the ``region`` parameter in the format ``[x_start, x_end, y_start, y_end]``,
 # where the date range is plotted on the x-axis. An additional notable
-# parameter is ``style``, where it's specified that data points are to be
-# plotted in an **X** shape with a size of 0.3 centimeters.
+# parameter is ``style``, where it's specified that data points are plotted
+# as circles with a diameter of 0.3 centimeters.
 
 x = [
     datetime.date(2010, 6, 1),
@@ -47,7 +47,7 @@
     frame=["WSen", "afg"],
     x=x,
     y=y,
-    style="x0.3c",
+    style="c0.3c",
     pen="1p",
 )
 fig.show()