from datetime import datetime, timedelta


TODAY = datetime.now().date()


def years_ago(date, years=25):
    try:
        date_past = date.replace(year=date.year-years)
    except ValueError:
        date_past = date.replace(year=date.year-years, day=date.day-1)
    return date_past


for n in range(5*365):
    date_future = TODAY + timedelta(days=n)
    date_past = years_ago(date_future)