How to truncate the time on a datetime object? – Dev

The best answers to the question “How to truncate the time on a datetime object?” in the category Dev.

QUESTION:

What is a classy way to way truncate a python datetime object?

In this particular case, to the day. So basically setting hour, minute, seconds, and microseconds to 0.

I would like the output to also be a datetime object, not a string.

ANSWER:

Use a date not a datetime if you dont care about the time.

>>> now = datetime.now()
>>> now.date()
datetime.date(2011, 3, 29)

You can update a datetime like this:

>>> now.replace(minute=0, hour=0, second=0, microsecond=0)
datetime.datetime(2011, 3, 29, 0, 0)

ANSWER:

I think this is what you’re looking for…

>>> import datetime
>>> dt = datetime.datetime.now()
>>> dt = dt.replace(hour=0, minute=0, second=0, microsecond=0) # Returns a copy
>>> dt
datetime.datetime(2011, 3, 29, 0, 0)

But if you really don’t care about the time aspect of things, then you should really only be passing around date objects…

>>> d_truncated = datetime.date(dt.year, dt.month, dt.day)
>>> d_truncated
datetime.date(2011, 3, 29)

ANSWER:

You cannot truncate a datetime object because it is immutable.

However, here is one way to construct a new datetime with 0 hour, minute, second, and microsecond fields, without throwing away the original date or tzinfo:

newdatetime = now.replace(hour=0, minute=0, second=0, microsecond=0)

ANSWER:

Four years later: another way, avoiding replace

I know the accepted answer from four years ago works, but this seems a tad lighter than using replace:

dt = datetime.date.today()
dt = datetime.datetime(dt.year, dt.month, dt.day)

Notes

  • When you create a datetime object without passing time properties to the constructor, you get midnight.
  • As others have noted, this assumes you want a datetime object for later use with timedeltas.
  • You can, of course, substitute this for the first line: dt = datetime.datetime.now()