Your actual period information is valuable to Premom’s advanced algorithm because it is an important part to how the app predicts your ovulation. It will also need other input, such as OPK results or BBT logs, but the app cannot work without your logged period record.
Citations:
1. Wideman L, Montgomery MM, Levine BJ, Beynnon BD, Shultz SJ. Accuracy of calendar-based methods for assigning menstrual cycle phase in women. Sports Health. 2013 Mar;5(2):143-9. doi: 10.1177/1941738112469930. PMID: 24427382; PMCID: PMC3658377.
2. Wilcox AJ, Dunson D, Baird DD. The timing of the "fertile window" in the menstrual cycle: day specific estimates from a prospective study. BMJ. 2000 Nov 18;321(7271):1259-62. doi: 10.1136/bmj.321.7271.1259. PMID: 11082086; PMCID: PMC27529.