timedemo.py

from datetime import datetime, timedelta

# datetime objects represent individual fixed points in time. If only
# the date component is needed, but not the hour, minute and seconds,
# you can use datetime.date instead.

now = datetime.today()
print(f"Current time in standard form is {now}.")

# datetime offers a handy method to insert its components into strings.
# Consult the documentation for other available %-placeholders.
print(now.strftime("Today is a %A. It is %B %d in the year %Y."))

# Objects of type timedelta represent time differences that can be added
# and subtracted to times. We can easily solve the "Gigasecond challenge"
# from the Code Wars katas with this functionality.

billion_seconds = timedelta(seconds=10**9)
gs_future = now + billion_seconds
print(f"A billion seconds from now, the time is {gs_future}.")
gs_past = now - billion_seconds
print(f"A billion seconds ago, the time was {gs_past}.")

# A datetime object can be created in many different ways.
ludwig = datetime(year=1770, month=12, day=17)
# Adding datetime objects would be nonsense, but subtracting them is a.
# meaningful thing. Time works analogous to temperatures in this sense.
elapsed = now - ludwig

print(f"Ludwig van Beethoven was born {elapsed.days} days ago.")

earlier_this_year = now.month < ludwig.month
earlier_this_month = now.month == ludwig.month and now.day <= ludwig.day

# (Converting a truth value to an int produces either 0 or 1.)
year_offset = int(not(earlier_this_year or earlier_this_month))
to_wait = datetime(now.year + year_offset, ludwig.month, ludwig.day) - now

# Three-step decision ladder to choose from three possibilities.
if to_wait.days == 0:
    print("Rejoice with celebration of Ludwig van Beethoven!")
elif to_wait.days == 1:
    print("Sleep tight thinking of Ludwig van Beethoven tomorrow!")
else:
    print(f"Still {to_wait.days} days until Ludwig van Beethoven's birthday!")