Complex sentence: The first ZAVNOBiH session began in Mrkonjić Grad on 25 November 1943 at 7 p.m. and completed the same night (26 November) at 4 o'clock in the morning.
Split into simpler sentences: The first ZAVNOBiH session began in Mrkonjić Grad on 25 November 1943 in 19 hours. Completed the same night (26 November) at 4 o'clock in the morning.