Seconds until end of day in python

There’s another question here that asks how many seconds since midnight – this question is the opposite.

How do I get the seconds until the end of the day, from the current time, using python?

Answer

The cleanest way I found to accomplish this is

def time_until_end_of_day(dt=None):
    # type: (datetime.datetime) -> datetime.timedelta
    """
    Get timedelta until end of day on the datetime passed, or current time.
    """
    if dt is None:
        dt = datetime.datetime.now()
    tomorrow = dt + datetime.timedelta(days=1)
    return datetime.datetime.combine(tomorrow, datetime.time.min) - dt

Taken from http://wontonst.blogspot.com/2017/08/time-until-end-of-day-in-python.html

This however, is not the fastest solution – you can run your own calculations to get a speedup

def time_until_end_of_day(dt=None):
    if df is None:
        dt = datetime.datetime.now()
    return ((24 - dt.hour - 1) * 60 * 60) + ((60 - dt.minute - 1) * 60) + (60 - dt.second)

timeit results:

Slow: 3.55844402313 Fast: 1.74721097946 (103% speedup)

As pointed out by Jim Lewis, there is a case where this faster function breaks on the day daylight savings starts/stops.