The date fields are all timestamps (total number of seconds since the start of the epoch 2001-01-01 00:00)

So you need to get the moments at which today started and will end, and filter for cases where (dateToStart >= MidnightLastNight) and (dateToStart < MidnightToNight)

Or if 'today' and 'tomorrow' are predefined with midnight values, where (dateToStart >= today, and dateToStart <= tomorrow)