Requirements for keeping track of business mileage?

[Jazmine S.]

I see a lot of articles that state you can use an app to track your miles, however it also always mentions in other sections that the IRS requires that you keep track of your miles as they are occurring, not weeks later etc. Is there anyone out there that has kept track of their miles using solely an app? If so what have your experiences been?

I suppose that maybe an app would show what day/time the record was created... But if not, it seems it would be hard to prove that something was entered way back in January, versus a few days prior to tax time.