Error: Non-integer years and months are ambiguous and not currently supported

When installing my custom app to sites I got this error message:

Non-integer years and months are ambiguous and not currently supported

It seems (I’m not sure) happened after I updated to new version:
erpnext 12.28.0 → 12.31.0
frappe 12.25.0 → 12.28.0

It worked with the old versions but now failed.
I have imported some module from frappe related to dates:

from frappe.utils.data import today, date_diff, add_months, add_days

Is there any change to this modules?

Where can I find the detail of the error (which file and line causing this)?
Thank you