Python returns the date before the given time

import datetime
# Get the current time 
today = datetime.datetime.now()
# Day of the week 
week_day=datetime.date.isoweekday(today)
# Calculate the offset Minus weeks 
now_offset = datetime.timedelta(days=-week_day)
# Three day offset 
day_offset_3=datetime.timedelta(days=-3)
# Three days ago 
day_before_3=(today + now_offset).strftime('%Y-%m-%d')
# Return to last year's time 
year_offset = datetime.timedelta(days=(-365-week_day))
# Get the time of the desired date 
now_time=(today + now_offset).strftime('%Y-%m-%d')
# Return to last year's date 
year_time = (today + year_offset).strftime('%Y-%m-%d')