time. Person-time is the sum of total time contributed by all subjects. The unit for person-time in this study is person-days (p-d). Time contributed by each subject: Subject A: 53 days Subject B: 70 days Subject C: 24 days Subject D: 70 days Subject E: 19 days Total person-days in the study: 53+70+24+70+19=236 person-days
https://sph.unc.edu/wp-content/uploads/sites/112/2015/07/nciph_ERIC4.pdf