Convert date to datetime in Python

747
votes

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)?

10
pythondatetimedate
Not a silly question; date objects should have a .datetime() method; what's silly is that they don't have such a method. – Zags
@Zags: or datetime.from_date() constructor. – jfs
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
@Dalore Daylight savings time is between 1am and 2am to avoid exactly the problem you are describing. – Zags
@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. – dalore

10 Answers

951
votes

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())
157
votes

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.

97
votes

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."

51
votes

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

args = d.timetuple()[:6]
datetime.datetime(*args)
10
votes

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...

7
votes

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')
4
votes

You can use easy_date to make it easy:

import date_converter
my_datetime = date_converter.date_to_datetime(my_date)
1
votes

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)
-10
votes

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

-13
votes

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