A cycle date is an 8 digit number found on your return transcripts. This date indicates the 4 digit tax year, two digit processing week, and two digit processing day of your return. IRS weeks run as follows

01 = Friday – Daily Account
02 = Monday – Daily Account
03 = Tuesday – Daily Account
04 = Wednesday – Daily Account
05 = Thursday – Weekly Account

A cycle code of 20170505, for example, would mean your return was processed as of the 5th day of the 5th week of 2017. In real dates that would equal to February 2nd, 2017.

The Cycle Code date is the date your return generated into the IRS system.