Not 어젯밤? Again I feel I've rarely heard this. I welcome other opinions.
어젯밤 is also accepted. 지난밤 and 어젯밤 are synonymous.
I believe 어젯밤 is more common
지난+밤 = last + night, 어젯+밤 = yesterday + night, i think..
Is 지난밤 not a catch-all for "past night?" It is, after all, just a 밤 that 지났다.