Today, the 13th of August is celebrated as Sri Krishna Janma Ashtami, as per the lunar calendar. Under this system, Lord Krishna’s birthday is celebrated on the 8th day of the second half (Krishna Paksha) of Shravana Masa.
Many people, including yours truly, follow the Solar calendar in celebrating the birth of Lord Krishna, which is called as Krishna Jayanti. This year, Sri Krishna Jayanti falls on September. As per Jayanti Nirnaya written by Srimadacharya, Krishna Jayanti is to be celebrated on Ashtami day when Rohini nakshatra occurs at midnight. The same combination occurs on September 11.
Anyways, it is just another opportunity for prayer to Lord Krishna. May HE bless us all!