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Convert date to datetime in Python

Is there a built-in method for converting a date to a datetime in Python, for example getting the datetime for the midnight of the given date? The opposite conversion is easy: datetime has a .date() method.

Do I really have to manually call datetime(d.year, d.month, d.day)?

Not a silly question; date objects should have a .datetime() method; what's silly is that they don't have such a method.
@Zags: or datetime.from_date() constructor.
no it shouldn't a date is a subset of datetime (it's even in the name). It's unambiguous what the date is from a datetime. But the other way round, a date is a block of 24h (usually), so it can have many datetimes. What datetime would come from a date? You can't always so 00:00 because what if that time doesn't exist, like for example daylight savings skipped it. Not so easy#
@Dalore Daylight savings time is between 1am and 2am to avoid exactly the problem you are describing.
@zags it all depends on the timezone source and destination, you can have a daylight savings time change at 1am but that would correspond to a midnight change in some other timezone. and if you're programming which timezone are you using? you could very well end up trying to get a time that doesn't exist. My point still stands, adding a time to a date is not straight forward. Then you also got to consider is your new datetime also timezone aware or naive.

a
apaderno

You can use datetime.combine(date, time); for the time, you create a datetime.time object initialized to midnight.

from datetime import date
from datetime import datetime

dt = datetime.combine(date.today(), datetime.min.time())

Thanks. Combined with the fact that time() returns (0,0) I think this comes out the cleanest: datetime.combine(d, time())
Just be careful not to let your code get datetime.time() confused with time.time(). Qualified names FTW!
Yes, good point. Fortunately, combine() raises an exception if you pass in a time.time or anything else other than a datetime.time.
For midnight, there's a python constant at either datetime.time.min (2.7.1+) or datetime.min.time() (older python)
Good solution, but I don't think datetime.min.time() is the cleanest way of getting a 00:00:00 time. That is because what it does is first retrieving the minimum value representable by datetime and then getting its time component. Incidentally, datetime.min = datetime(MINYEAR, 1, 1, tzinfo=None) and has a time of 00:00:00. However, I think it is cleaner to explicitly create a 00:00:00 time either through time.min or time(0, 0, 0, 0).
A
Alex Martelli

There are several ways, although I do believe the one you mention (and dislike) is the most readable one.

>>> t=datetime.date.today()
>>> datetime.datetime.fromordinal(t.toordinal())
datetime.datetime(2009, 12, 20, 0, 0)
>>> datetime.datetime(t.year, t.month, t.day)
datetime.datetime(2009, 12, 20, 0, 0)
>>> datetime.datetime(*t.timetuple()[:-4])
datetime.datetime(2009, 12, 20, 0, 0)

and so forth -- but basically they all hinge on appropriately extracting info from the date object and ploughing it back into the suitable ctor or classfunction for datetime.


Very good point. datetime(d.year, d.month, d.day) does seem much more readable than the accepted answer datetime.combine(d, datetime.min.time()).
@SimonTewsi: midnight = datetime.datetime.combine(d, datetime.time.min) seems cleaner (suggested by @larham1)
@J. F. Sebastian: It is somewhat cleaner but I agree with Wes Winham in his answer that it requires the reader to know what datetime.time.min represents. Whereas it seems to me that datetime(d.year, d.month, d.day) is more obvious (a datetime without the time component). It's a minor point, though, and using a variable name like "midnight" makes it obvious what the result is even if the reader doesn't know what datetime.time.min represents.
Another variant just for fun: datetime.datetime(*(getattr(d, attr) for attr in ("year", "month", "day"))). That way, you can easily modify the list of attributes that matter to you. Hours could be added dynamically for example.
W
Wes Winham

The accepted answer is correct, but I would prefer to avoid using datetime.min.time() because it's not obvious to me exactly what it does. If it's obvious to you, then more power to you. I also feel the same way about the timetuple method and the reliance on the ordering.

In my opinion, the most readable, explicit way of doing this without relying on the reader to be very familiar with the datetime module API is:

from datetime import date, datetime
today = date.today()
today_with_time = datetime(
    year=today.year, 
    month=today.month,
    day=today.day,
)

That's my take on "explicit is better than implicit."


And a hat tip to Kyle Gibson for the original idea: stackoverflow.com/users/513197/kyle-gibson
I agree with your sentiment. All these other answers with timetuple and asterisks and min.time() require research, and the Python way of handling dates and datetimes is a bit cumbersome anyway compared to the ease that Microsoft handles them in VBA. It as simple as wrapping them in hash symbols in that language. But I digress.
d2dt = lambda date: datetime(year=date.year, month=date.month, day=date.day) on-liner function of this answer.
This works, but you may need the datetime to be timezone aware. In which case, you can import pytz and then add tzinfo=pytz.timezone('Europe/London'), for example.
N
Nam G VU

You can use the date.timetuple() method and unpack operator *.

args = d.timetuple()[:6]
datetime.datetime(*args)

This is useful for my situation. I don't know if it's a date or a datetime I'm being passed, and it's not very pythonic to check which class it is. This method looks like it will work for both datetime and date objects.
I used to use this before discovering datetime.combine via @kiamlaluno's answer. I think it's fairly pythonic, especially given constructing a datetime.time object is likely to look something like datetime.time(*map(int,"H:M:S".split(":"))) anyway...
useful in many other contexts too for example truncating seconds, minutes, or hours by indexing down to as low as [:3] and even lower if you pad with + (n,) as in : dt.datetime(*(dt.datetime.utcnow().timetuple()[:2] + (1, )))
k
kadee

Today being 2016, I think the cleanest solution is provided by pandas Timestamp:

from datetime import date
import pandas as pd
d = date.today()
pd.Timestamp(d)

Timestamp is the pandas equivalent of datetime and is interchangable with it in most cases. Check:

from datetime import datetime
isinstance(pd.Timestamp(d), datetime)

But in case you really want a vanilla datetime, you can still do:

pd.Timestamp(d).to_datetime()

Timestamps are a lot more powerful than datetimes, amongst others when dealing with timezones. Actually, Timestamps are so powerful that it's a pity they are so poorly documented...


Good call. Came here as I thought it would need a python datetime solution to a pandas DatetimeIndex issue. Shame pandas doesn't have the concept of a DateIndex.
why do we require a heavyweight package just to do datetime manipulation, even in 2016?!
Bringing out pandas for this is like taking a hammer to an ant
using pandas to solve this problem is major overkill
k
kadee

One way to convert from date to datetime that hasn't been mentioned yet:

from datetime import date, datetime
d = date.today()
datetime.strptime(d.strftime('%Y%m%d'), '%Y%m%d')

True, but converting ints to strings and back is probably rather more expensive than working directly with ints, so I'd only use this one for low-volume processing
N
NONONONONO

you can also use

date = datetime.utcnow().date()
dt = datetime.fromisoformat(date.isoformat())

print(dt)

datetime.datetime(2021, 11, 15, 0, 0)


You can even add the time as a string in this way: datetime.fromisoformat(date.isoformat() + ' 17:32')
R
Raphael Amoedo

You can use easy_date to make it easy:

import date_converter
my_datetime = date_converter.date_to_datetime(my_date)

S
Sławomir Lenart

Do I really have to manually call datetime(d.year, d.month, d.day)

No, you'd rather like to call

date_to_datetime(dt)

which you can implement once in some utils/time.py in your project:

from typing import Optional
from datetime import date, datetime

def date_to_datetime(
    dt: date,
    hour: Optional[int] = 0,
    minute: Optional[int] = 0, 
    second: Optional[int] = 0) -> datetime:

    return datetime(dt.year, dt.month, dt.day, hour, minute, second)

Probably an idea to add tz to that
better, as this will be quicker than converting to string and back
o
ont.rif

You can use this class:

import time 

import datetime

class TimingClass():

    def __init__(self):

        self.YEAR        = datetime.date.today().year
        self.MONTH       = datetime.date.today().month
        self.DATE        = datetime.date.today().day
        self.HOUR        = datetime.datetime.now().hour
        self.MINUTE      = datetime.datetime.now().minute
        self.SECONDS     = datetime.datetime.now().second
        
        self.TODAY       = datetime.date.today()
        self.YESTERDAY   = datetime.datetime.strftime( (self.TODAY - datetime.timedelta(days = 1)) , '%Y-%m-%d')
        self.TOMORROW   = datetime.datetime.strftime( (self.TODAY + datetime.timedelta(days = 1)) , '%Y-%m-%d')
        
        self.TODAY_datetime = datetime.datetime.combine(datetime.date.today(), datetime.datetime.min.time())

d
dqd

To make dt timezone aware datetime (with Django timezone util):

from django.utils import timezone


timezone.now().replace(*(*dt.timetuple()[:6], 0))

a
apaderno

If you need something quick, datetime_object.date() gives you a date of a datetime object.


the op wants the opposite, to go from date to datetime.
From the question: The opposite conversion is easy: datetime has a .date() method., bold emphasis mine.
n
napier

I am a newbie to Python. But this code worked for me which converts the specified input I provide to datetime. Here's the code. Correct me if I'm wrong.

import sys
from datetime import datetime
from time import mktime, strptime

user_date = '02/15/1989'
if user_date is not None:
     user_date = datetime.strptime(user_date,"%m/%d/%Y")
else:
     user_date = datetime.now()
print user_date

The OP has a datetime.date() object, not a string.