Steps to reproduce:

1. Changes in configuration... – none
2. Navigate to screen title... any graph
3. Click on screen element...included time interval (last 3 hours, today so far, etc.)
4. ...

Result:
See screenshot...
See log file...
See memory dump...
Expected:
See screenshot....  Three different screen images taken all within the same 5-minute interval, but with different time spans selected.  Notice how when "longer" time spans are displayed, the data shown on the graph is less current.   For example, the first image, zabbix1.jpg was collected first and contains data up through 13:29 which was very near current time.  The last image, zabbix3.jpg which was captured AFTER zabbix1, only contains data up through 06:00.
See attached patch file...