The Problem

“A countdown of victims that will end at midnight unless our dear Dark Knight stops me first!” - Joker in Holiday Knights

Imagine you need to know the number of seconds from now until midnight. It could help Batman save Gotham. It could also help a web developer (like me) cache some data in Redis that should self-destruct at the end of the day. How would you do it?

My Solution

As always, I turn to Python. But it doesn’t solve my problem instantly. Python has many ways to deal with date math – should I use datetime? date? time? timedelta? An external library like dateutil?

Well, for best readability, I decided on a mixture that is pure Python with no external modules:

from datetime import datetime, timedelta

def how_many_seconds_until_midnight():
    """Get the number of seconds until midnight."""
    tomorrow = datetime.now() + timedelta(1)
    midnight = datetime(year=tomorrow.year, month=tomorrow.month, 
                        day=tomorrow.day, hour=0, minute=0, second=0)
    return (midnight - datetime.now()).seconds

Or, if you want to remove the timedelta dependency and just use math:

from datetime import datetime

def how_many_seconds_until_midnight():
    """Get the number of seconds until midnight."""
    n = datetime.now()
    return ((24 - n.hour - 1) * 60 * 60) + ((60 - n.minute - 1) * 60) + (60 - n.second)