Python numpy: cannot convert datetime64[ns] to datetime64[D] (to use with Numba)

Question

I want to pass a datetime array to a Numba function (which cannot be vectorised and would otherwise be very slow). I understand Numba supports numpy.datetime64. However, it

Answer 1

Ran into the same error when calculating number of business days between two dates:

from pandas.tseries.offsets import MonthBegin
import numpy as np 

# Calculate the beginning of the month from a given date
df['Month_Begin'] = pd.to_datetime(df['MyDateColumn'])+ MonthBegin(-1)

# Calculate # of Business Days
# Convert dates to string to prevent type error [D]
df['TS_Period_End_Date'] = df['TS_Period_End_Date'].dt.strftime('%Y-%m-%d')
df['Month_Begin'] = df['Month_Begin'].dt.strftime('%Y-%m-%d')

df['Biz_Days'] = np.busday_count(df['Month_Begin'], df['MyDateColumn']) #<-- Error if not converted into strings.

My workaround was to convert the dates using ".dt.strftime(''%Y-%m-%d')". It worked in my particular case.