Finding the min of a range of cells that correspond to specific dates

I have a very lengthy list of cells that contain dates and corresponding speeds. There are multiple speeds for every day because it is hourly data. I need to find a way to find the maximum speed of every day and paste it to another column R.

Something like "if date = 01/01/2000 then cells (i,"R") = minimum speed for that day and so on for every date in my sheet.

this is for i = 2 to 150000 (i being the number of rows of data)

sample of the how the sheet looks

Spd ---- Date

12 ----- 01/01/2000

18------ 01/01/2000

11 ------ 01/01/2000

13 ----- 01/02/2000

31 ----- 01/02/2000

44 ----- 01/02/2000