This is due to the database issue in 5.9.20. If he has data that is NOT synced, go to the Contact Us area of the app and submit a problem report. I can recover the data and send unsynced information to his cloud sync portal. Nothing is lost, it's just a date conversion issue. Once he has submitted the problem report OR has no unsynced data you have to delete the app and reinstall 5.9.30 from the App Store which will rebuild the database to the correct format.
What people do not realize with Logbook Pro Mobile is that once data is synced it is meaningless and should be purged. Sync, verify it's in your PC, then tap the trash can button in the app and choose "Delete Synced".
So again, he will not lose anything. If unsynced data needs to be recovered and sent to the PC just submit the problem report and I can quickly handle it.