Steps to reproduce:

1. Go to problems page
2. Select "History" value for "Show" field
3. Apply filter
4. Open filter tab with date/time
5. Type invalid date format, for example, type "abc" in "Form" field
6. Apply filter, get error message "invalid date."
7. Select "Filter" tab
8. Apply filter

Result:

Fatal error, please report to the Zabbix team
- Incorrect value for field "from": a time is expected.
- Controller: problem.view
- action: problem.view
- filter_application:
....

On pages Reports -> Availability report, 100 busiest triggers, Audit log the result is without fatal error, but with message "Zabbix has received an incorrect request."