Thank you for your post.
Get (CurrentDate) uses the current date of the client machine; not FileMaker Server.. With FileMaker Go, this would be the iOS device (iPad in your case). For some unbeknownst reason, FileMaker Go is seeing the current year as 1980. I know the issue is sporadic, so the next time this occurs, write down all applications open at the time, and the length of time since the iPad was last rebooted. This may help narrow the possible causes.