Adjusting X Axis formatting

hey everyone. im having a slight issue with my report, so as you see in the photos, my line chart's X axis is taking data from a field parameter called granularity, which basically has 3 columns, 'day' for daily view, '15 min' to view each 15min and 'hour' for hourly view. 
at first i had the formats for those columns as a long time format 01:30 PM. but then i realised that i still need to see the day/month in the 15 minutes and hour granularities. i added a "DMY" column as you can see in the bottom photo which has date in the format dd-mmm-yy, and that is exactly how i want it to be. but the thing is if i change between my field parameters, the value for the x axis will then take only the DMY column as my x axis data and won't change anymore if i change my field parameter again.  i added a 3rd image that shows how when i changed the granularity to hour, it changed based on the dmy.

what can i do to get the results in the second photo, while maintaining the functionality of my field parameter?

without DMY

with DMY

after changing granularity