days_since(signup, today) where both arguments are datetime.date objects, returning the whole number of days between them. Subtracting two dates yields a timedelta — read its .days.days_since(date(2026, 7, 1), date(2026, 7, 28))
27
The timedelta between the dates spans 27 days.
today - signup produces a timedelta.
.days extracts the integer.