Shaban-ul-Moazzam dates of significance

English: Zarih_of_Imam Husain,Karbala (Photo credit: Wikipedia)

From ziyaraat.net:

Some important events of the 8th Islamic month are as follows:

1st - Birth of Hazrat Zainab (S.A.) – 5 A.H.
3rd - Birth of Imam Hussain (A.S.) – 4 A.H.
4th - Birth of Hazrat Abbas (A.S.) – 26 A.H.
5th - Birth of Imam Zain al-Abideen (A.S.) – 38 A.H.
7th - Birth of Hazrat Qasim ibn-e-Hasan (A.S.)
8th - Start of Ghaibat-e-Sughra of Imam Zamana (A.S.) – 260 A.H.
11th - Birth of Hazrat Ali Akbar (A.S.) – 44 A.H.
13th, 14th and 15th – Ayyam-e-Bayz – the bright days
15th night – Aamal of Neema-e-Shabaan (middle of Shabaan)
15th - Birth of Imam Zamana (A.S.) – 255 A.H.
Last 3 days - Fasting highly recommended

Resources

The Month of Shaban - Source: qFatima.com
Rites of the Month of Shaban - Source A.Q.R.