In the Morean War, the Republic of Venice besieged Sinj in October 1684 and then again March and April 1685, but both times without success. In the 1685 attempt, the Venetian armies were aided by the local militia of the Republic of Poljica, who thereby rebelled against their nominal Ottoman suzerainty that had existed since 1513. In an effort to retaliate to Poljica, in June 1685, the Ottomans attacked Zadvarje, and in July 1686 Dolac and Srijane, but were pushed back, and suffered major casualties. With the help of the local population of Poljica as well as the Morlachs, the fortress of Sinj finally fell to the Venetian army on 30 September 1686. On 1 September 1687 the siege of Herceg Novi started, and ended with a Venetian victory on 30 September. Knin was taken after a twelve-day siege on 11 September 1688. The capture of the Knin Fortress marked the end of the successful Venetian campaign to expand their territory in inland Dalmatia, and it also determined much of the final border between Dalmatia and Bosnia and Herzegovina that stands today. The Ottomans would besiege Sinj again in the Second Morean War, but would be repelled. On 26 November 1690, Venice took Vrgorac, which opened the route towards Imotski and Mostar. In 1694 they managed to take areas north of the Republic of Ragusa, namely Čitluk, Gabela, Zažablje, Trebinje, Popovo, Klobuk and Metković. In the final peace treaty, Venice did relinquish the areas of Popovo polje as well as Klek and Sutorina, to maintain the pre-existing demarcation near Ragusa.
Question: What date did the siege on Knin begin?
Answer: 31 August 1688