Ok, now I understand your problem. I think the easiest would be to directly modify your URL:
https://[nameofthehost]/dashboards#/{...}time:(from:now%2Fd-12h,to:now%2Fd-12h)){...}
The bold part is what you need to use.
The value now%2Fd-12h is an escaped value for now/d-12h.Firstly we round 'now' to a day now/d (which gives us the 00:00:00 today) and then we subtract 12 hours (which gives us noon yesterday). The closing value will give us 23:59:59 today and we get 11:59:59 today after subtraction. If you need something more complicated, take a look at the docs: