Irregular cycle

Hi my cycle has been kind of irregular the past few months.  Does glow calibrate its ovulation and menstrual cycle accordingly? For example in my settings I have my average cycle to be 30 days . Two months ago I've been getting it every 28 days and this month I got it early on the 26th day!  Confusing.  Am I supposed to change the setting each time? Or does glow automatically adjust for me?