In both sandbox and production, no report can be customized or created as all date filters or date entries read as
invalid date. Locale is US English
Fails - new or customize any report
Also - If you select a date from the date picker, no date is populated (or is invisible)
Works - run existing reports
Existing reports will execute and their date filters can be changed from the Report page but they can't be customized; no new reports can be created.
Looks like a SFDC bug to me.
Anyone else seen this?
UPDATE - Now a Known Issue - has nothing to do with Fiscal year change. I removed all refs to fiscal year in OP
UPDATE 2 - Now fixed see Known Issue - a rather rapid SFDC fix I might say.