Time encoding for xarray to netCDF

While looking at this webpage, it seems there is an inconsistency for the time units handling.

Copying and pasting from the webpage:

from cftime import date2num
time_units = 'hours since {:%Y-%m-%d 00:00}'.format(times[0])
time_vals = date2num(times, time_units)

ds = xr.Dataset({'temperature': (['time', 'z', 'y', 'x'], temps, {'units':'Kelvin'})},
                 coords={'x_dist': (['x'], x, {'units':'km'}),
                         'y_dist': (['y'], y, {'units':'km'}),
                         'pressure': (['z'], press, {'units':'hPa'}),
                         'forecast_time': (['time'], times)
                })

ds.forecast_time.encoding['units'] = time_units

hence it seems that time_vals and not times should be assigned to forecast_time.