Eve says late period?

Sara
Last month I was late by a week bc of stress and I got my period on the 13th,  and now <a href="https://play.google.com/store/apps/details?id=com.glow.android.eve">Eve</a>'s telling me I'll get mine on the 20th? I usually have a 30 day cycle and my past periods (excluding last month) have been pretty normal