App not working in rare cases

[Vikath]

When a datetime ending without milliseconds is written in logs/accounting.json, the app stars on crash with a FormatError. T didn't log the error message :(

Maybe don't save the milliseconds at all?

[mostley]

@Vikath please test this

[mostley]

was fixed with 95339df0c6fc5298338f5aa92555451119468423