How to fix angular js undefined error?

Question

I have an index.cshtml and im using angular js libraries directly and somehow its getting this undefined error message below;

angular.js:13236 TypeError: Cannot read properties of undefined (reading 'substr')
at ConvertJsonDateToDateTime (Index:70)
at Index:60
at angular.js:10973
at angular.js:15552
at m.$eval (angular.js:16820)
at m.$digest (angular.js:16636)
at m.$apply (angular.js:16928)
at g (angular.js:11266)
at t (angular.js:11464)
at XMLHttpRequest.u.onload (angular.js:11405)