Incrementing time represented as NBCD format

[Blitz]

Here's my best shot

Code:

function nbcdTimeIncr ( byval t as integer ) as integer
    t1 = t + &ha6a7
    m1 = t  and &h11110
    m2 = t1 and &h11110
    
    nbcdTimeIncr =  t1 - ((((not (m1 xor m2)) and &h11110) shr 4)*&hf and &ha6a6)
end function

Add AND &hffff if you care that the upper 16 bits are zero or not.