^^ Yes, in South East Asia we started fasting on August 11th. So yes, last night was the 21st night of Ramadhaan.
Now that you know when it starts, you still have the other odd num of nights (23rd, 25th, 27th, 29th) to try to find the Layl al-Qadr and increase our I'baadah during the last 10 days of Ramadhaan, inshaAllaah.
AbuBakrah heard Allah’s Messenger (saw) say, ” Seek it (meaning Laylat al-Qadr), on the twenty-first, twenty-third, twenty-fifth, twenty-seventh, or on the last night.”
Hadith – Al-Tirmidhi #2096, Narrated Anas ibn Malik [Bayhaqi transmitted it in Shu'ab al-Iman.]