USCIS announced that starting on January 4, 2017, it will post processing times using specific dates, instead of weeks or months. USCIS says this is the first step in providing more timely and easier to understand processing times for applicants.
Processing times are posted on the USCIS website. In the past, two different formats have been used.
Always refer to the I-797C, Notice of Action, and look for "receipt date" to determine when USCIS accepted your case. If the receipt date online is after the date listed on your notice, you can expect to hear from USCIS shortly.