Iterating datetime field in a numpy array

Question

I have a numpy array that looks like below. I wanted to pull out the data day by day and run a function on that. I tried doing it brute force (code snippet below) but that does not quite work either. I'm sure there is a function of some sort that will just pull out the parts of array that correspond to particular day and pass that subset to my function:

while i < len(stoch_osc):
    print('value of i is: ', i, ' Valuate of i+delta is: ', i + delta)
    print(stoch_osc[i:i + delta, ])
    some_function(stoch_osc[i:i + delta, ])
    i = i + delta

stoch_osc is an array that looks like this (timestamp in datetime 
followed by a bunch of values).  I get below output by doing print(stoch_osc):
 
[[Timestamp('2021-10-01 00:32:00') 4276.0 4276.0 ... 4275.25 83 64.28]

 [Timestamp('2021-10-01 00:33:00') 4275.5 4276.25 ... 4276.25 105 78.57]

 [Timestamp('2021-10-01 00:34:00') 4276.25 4276.75 ... 4275.5 10167.85]

 [Timestamp('2021-10-04 01:31:00') 4331.0 4333.0 ... 4332.25 582 71.21]]