When creating payslip error

[khalloda]

Odoo version: 12.0-20181015
OpenHRMS: Latest on this gethub for v12

Odoo Server Error
Traceback (most recent call last):
File "C:\Program Files (x86)\Odoo 12.0\server\odoo\http.py", line 653, in _handle_exception
return super(JsonRequest, self)._handle_exception(exception)
File "C:\Program Files (x86)\Odoo 12.0\server\odoo\http.py", line 312, in _handle_exception
raise pycompat.reraise(type(exception), exception, sys.exc_info()[2])
File "C:\Program Files (x86)\Odoo 12.0\server\odoo\tools\pycompat.py", line 87, in reraise
raise value
File "C:\Program Files (x86)\Odoo 12.0\server\odoo\http.py", line 695, in dispatch
result = self._call_function(**self.params)
File "C:\Program Files (x86)\Odoo 12.0\server\odoo\http.py", line 344, in _call_function
return checked_call(self.db, *args, **kwargs)
File "C:\Program Files (x86)\Odoo 12.0\server\odoo\service\model.py", line 97, in wrapper
return f(dbname, *args, **kwargs)
File "C:\Program Files (x86)\Odoo 12.0\server\odoo\http.py", line 337, in checked_call
result = self.endpoint(*a, **kw)
File "C:\Program Files (x86)\Odoo 12.0\server\odoo\http.py", line 938, in call
return self.method(*args, **kw)
File "C:\Program Files (x86)\Odoo 12.0\server\odoo\http.py", line 517, in response_wrap
response = f(*args, **kw)
File "C:\Program Files (x86)\Odoo 12.0\server\odoo\addons\web\controllers\main.py", line 962, in call_kw
return self._call_kw(model, method, args, kwargs)
File "C:\Program Files (x86)\Odoo 12.0\server\odoo\addons\web\controllers\main.py", line 954, in _call_kw
return call_kw(request.env[model], method, args, kwargs)
File "C:\Program Files (x86)\Odoo 12.0\server\odoo\api.py", line 749, in call_kw
return _call_kw_multi(method, model, args, kwargs)
File "C:\Program Files (x86)\Odoo 12.0\server\odoo\api.py", line 736, in _call_kw_multi
result = method(recs, *args, **kwargs)
File "C:\Program Files (x86)\Odoo 12.0\server\odoo\models.py", line 5351, in onchange
record._onchange_eval(name, field_onchange[name], result)
File "C:\Program Files (x86)\Odoo 12.0\server\odoo\models.py", line 5273, in _onchange_eval
method_res = method(self)
File "C:\Program Files (x86)\Odoo 12.0\server\odoo\addons\ohrms_loan\models\hr_payroll.py", line 27, in onchange_employee
ttyme = datetime.fromtimestamp(time.mktime(time.strptime(date_from, "%Y-%m-%d")))
File "C:\Program Files (x86)\Odoo 12.0\python\lib_strptime.py", line 559, in _strptime_time
tt = _strptime(data_string, format)[0]
File "C:\Program Files (x86)\Odoo 12.0\python\lib_strptime.py", line 329, in _strptime
raise TypeError(msg.format(index, type(arg)))
TypeError: strptime() argument 0 must be str, not <class 'datetime.date'>