Fixing time values on graph

[sonic-boom]

I have attached the file I need help with. I want the x-axis from 00:30 to 08:00. And the range (or the major unit) be 30 minutes. (I just could not do it in time format). Any help will be appreciated.

[martindwilson]

major unit as 0.020833333 minimum as 0.020833333 should do it that is 00:30 and /or 30 minutes excel time code