Things get even more complicated when you consider time zones. Some systems store epoch dates as a signed 32-bit integer, which might cause problems on January 19, 2038 (known as the Year 2038 problem or Y2038). Here’s a selected list of articles and videos that I found helpful in writing this tutorial: In addition, Paul Ganssle is a core contributor to CPython and the current maintainer of dateutil. I have a time in UTC from which I want the number of seconds since epoch. For instance, you might provide a string with the year, month, and date specified: This string represents the date January 31, 2020, according to the ISO 8601 format. In this post you will learn how to do all sorts of operations with these objects and solve date-time related practice problems (easy to hard) in Python. Converting unix timestamp string to readable date, Convert UTC datetime string to local datetime, Old story about two cultures living in the same city, but they are psychologically blind to each other's existence. Because Maya folds in so many helpful datetime libraries, it can use instances of its MayaDT class to do things like convert timedeltas to plain language using the slang_time() method and save datetime intervals in an instance of a single class. Convert a string representing the date or epoch time to datetime and change timezone in Python. Timedeltas (made by subtracting two datetimes) have total_seconds, but datetimes do not. If the amount of time is not equal to zero, then time_amount() returns a string with the amount of time and the time unit. If possible avoiding to import other libraries unless standard. Contribute to alpacahq/alpaca-trade-api-python development by creating an account on GitHub. Since these objects are so useful, calendar also returns instances of classes from datetime. https://docs.python.org/3/library/datetime.html#datetime.datetime.fromisoformat. The %s directive is used for this purpose. What are the differences between an agent and a model? However, for historical and political reasons, time zone lines are rarely straight. However, the Python documentation recommends against using this method because it doesn’t include any time zone information in the resulting instance. Complaints and insults generally won’t make the cut here. I am using strftime to convert it to the number of seconds. However, this has only been the case since 2007. Join us and get access to hundreds of tutorials, hands-on video courses, and a community of expert Pythonistas: Master Real-World Python SkillsWith Unlimited Access to Real Python. This standard specifies that all dates should be written in order of most-to-least-significant data. However, timezone is limited to expressing fixed offsets from UTC that cannot change throughout the year, so it isn’t that useful when you need to account for changes such as daylight saving time. However, until Python 3.9 becomes widely used, it probably makes sense to rely on dateutil if you need to support multiple Python versions. In this section, you’ll use relativedelta to calculate the time remaining until PyCon, develop a function to print the time remaining in a nice format, and show the date of PyCon to the user. datetime.datetime(2020, 1, 31, 13, 14, 31), datetime.datetime(2020, 1, 24, 14, 4, 57, 10015), datetime.datetime(2020, 1, 24, 14, 4, 57), datetime.datetime(2020, 1, 31, 14, 45, 37), datetime.datetime(2020, 3, 13, 14, 39, 1, 350918), datetime.datetime(2020, 3, 15, 14, 39, 7, 314754), datetime.datetime(2020, 1, 26, 0, 55, 3, 372824, tzinfo=tzlocal()), datetime.datetime(2020, 1, 26, 6, 14, 53, 513460, tzinfo=tzfile('GB-Eire')), datetime.datetime(2020, 3, 14, 19, 1, 20, 228415, tzinfo=tzutc()), datetime.datetime(2020, 1, 26, 9, 37, 46, 380905), datetime.datetime(2020, 1, 27, 9, 37, 46, 380905), datetime.datetime(2020, 1, 25, 9, 37, 46, 380905), datetime.datetime(2020, 1, 29, 5, 37, 46, 380905), datetime.datetime(2025, 3, 1, 5, 7, 46, 380905), How Time Should Be Stored in Your Program, Using Strings to Create Python datetime Instances, Using dateutil to Add Time Zones to Python datetime, Comparing Naive and Aware Python datetime Instances, Using relativedelta in Your PyCon Countdown, Showing the PyCon Date in Your PyCon Countdown, Alternatives to Python datetime and dateutil, Click here to get our free Python Cheat Sheet, Computerphile: The Problem With Time & Timezones, Working With Time Zones: Everything You Wish You Didn’t Need to Know, Daylight saving time and time zone best practices, Coding Best Practices Using DateTime in the .NET Framework, Computerphile: The Problem with Time & Timezones, Working with Time Zones: Everything You Wish You Didn’t Need to Know, A curious case of non-transitive datetime comparison, Hour (as zero-padded decimal with 24-hour clock). Fortunately, datetime provides several other convenient ways to create datetime instances. Now that you understand more about how to measure time in seconds using an epoch, let’s take a look at Python’s time module to see what functions it offers that help you do so. If you already know all about this, then you can skip ahead to improve your PyCon countdown with time zone information. Note: If you want to learn more about why time can be so complicated to deal with, then there are many great resources available on the web. The way Python handles all that happen to be pretty confusing (to me). Viewed 360k times 236. site design / logo © 2021 Stack Exchange Inc; user contributions licensed under cc by-sa. Fortunately, dateutil provides a more powerful replacement called relativedelta. The epoch is the point where the time starts, and is platform dependent. However, relativedelta allows you to show the years, months, and days remaining: The only change that you made in this code was to replace line 11 with countdown = relativedelta(PYCON_DATE, now). These differences can cause all sorts of confusion when communicating across cultures. You can even provide a mix of positive and negative arguments. Thank you. Here’s an example of how .strptime() works: In this code, you import datetime on line 3 and use datetime.strptime() with date_string and format_string on line 4. As you saw earlier, this relies on using timedelta instances to represent time intervals. I have a time in UTC from which I want the number of seconds since epoch. You can try out this code to see how the alternate initializers work: In this code, you use date.today(), datetime.now(), and datetime.combine() to create instances of date, datetime, and time objects. To get started, create a file called pyconcd.py and add this code: In this code, you import datetime from datetime and define a constant, PYCON_DATE, that stores the date of the next PyCon US. timedelta is very useful in this way, but it’s somewhat limited because it cannot add or subtract intervals larger than a day, such as a month or a year. By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy. Complete this form and click the button below to gain instant access: © 2012–2021 Real Python ⋅ Newsletter ⋅ Podcast ⋅ YouTube ⋅ Twitter ⋅ Facebook ⋅ Instagram ⋅ Python Tutorials ⋅ Search ⋅ Privacy Policy ⋅ Energy Policy ⋅ Advertise ⋅ Contact❤️ Happy Pythoning! Why would collateral be required to make a stock purchase? What's the point of a MOSFET in a synchronous buck converter? On line 2, you create format_string, which uses the mini-language to specify how the parts of date_string will be turned into datetime attributes. Remember, you can find the formatting codes that you want to use on strftime.org. With the subtraction operator, your timedelta object couldn’t count intervals of time larger than a day. This means that at 03:14:07 on January 19, 2038, the integer will overflow, resulting in what’s known as the Year 2038 problem, or Y2038. You can read all about these other uses in the dateutil documentation. Python 3.9 includes a new module called zoneinfo that provides a concrete implementation of tzinfo that tracks the IANA database, so it includes changes like daylight saving time. The accepted answer does not work for dates less than 1970. Often, areas that are separated by large distances find themselves in the same time zone, and adjacent areas are in different time zones. dateutil.relativedelta objects have countless other uses. Convert python datetime to epoch with strftime, Converting datetime.date to UTC timestamp in Python, Python issue: datetime.strftime('%s') should respect tzinfo, http://docs.python.org/library/datetime.html#strftime-and-strptime-behavior, more issues with converting a local time (such as returned by, it doesn't answer the question unless the local timezone is UTC, https://docs.python.org/2/library/time.html#module-time, I followed my dreams and got demoted to software developer, Opt-in alpha test for a new Stacks editor, Visual design changes to the review queues, Converting DateTimeField in Django to Unix time, How to convert a date to Epoch time in python. Unsubscribe any time. The database contains a copy of all the designated time zones and how many hours and minutes they’re offset from UTC. You can install dateutil with pip: Note that the name of the package that you install from PyPI, python-dateutil, is different from the name that you use to import the package, which is just dateutil. The output from this script should tell you that PyCon US 2021 will happen in about one year and one month, depending on when you run the script. That is because time.mktime does not take into consideration the microsecond part, right? But what if you have a string that represents a date and time but isn’t in the ISO 8601 format? At the time of writing, this was March 13, 2020, at 2:39 PM. You also use tzname() to print the name of the time zone, which is now 'GMT', meaning Greenwich Mean Time. On line 1, you import dateparser. By definition, Unix time elapses at the same rate as UTC, so a one-second step in UTC corresponds to a one-second step in Unix time. In a later section, you’ll see how to assign time zone information to datetime instances. your coworkers to find and share information. First, time.time() returns the number of seconds that have passed since the epoch. One particularly neat library is called dateparser, which allows you to provide natural language string inputs. This allows other people to import your code and reuse PYCON_DATE, for instance, if they’d like. timedelta instances support addition and subtraction as well as positive and negative integers for all arguments. time is less powerful and more complicated to use than datetime. Now that you know how to add time zone information to a Python datetime instance, you can improve your PyCon countdown code. I thought datetime was purely naive? Martin Thoma. This the most accurate answer to me, if you are looking to convert your time in GMT and you want to keep it that way on the conversion to epoch timestamp. If you want to convert a python datetime to seconds since epoch you could do it explicitly: In Python 3.3+ you can use timestamp() instead: Why you should not use datetime.strftime('%s'). If no timezone is provided then returned object will contain the current date time information in local timezone. Earlier, you learned about creating datetime instances using .strptime(). You can update your code to use the dateutil.parser module, which provides a more natural interface for creating datetime instances: In this code, you import parser and tz from dateutil and datetime from datetime. To subscribe to this RSS feed, copy and paste this URL into your RSS reader. But aware instances are crucial if you’re comparing times with each other, especially if you’re comparing times in different parts of the world. An aware datetime instance has the tzinfo attribute equal to a subclass of the datetime.tzinfo abstract base class. You’ll see a little later on how you can use the ISO 8601 format with Python datetime. On my machines, this works correctly even though my time zone is ET. Finally, line 18 prints the final output using .join() on the generator. You can also create time zones that are not the same as the time zone reported by your computer. As you saw in the last example, Unix time is nearly impossible for a human to parse. You can differentiate between the two methods by remembering that the p in .strptime() stands for parse, and the f in .strftime() stands for format. Thank you for nothing this! Fortunately, Python datetime provides a method called .strptime() to handle this situation. I am using strftime to convert it to the number of seconds. However, that output isn’t very pretty since it looks like the signature of relativedelta(). Literally speaking the epoch is Unix time 0 (midnight 1/1/1970), but 'epoch' is often used as a synonym for Unix time. Warning: datetime also provides datetime.utcnow(), which returns an instance of datetime at the current UTC. datetime provides three classes that make up the high-level interface that most people will use: The three classes that represent dates and times in datetime have similar initializers. 相关术语的解释 2. This takes the hassle out of assigning time zones to your datetime instances. In many cases, especially when you’re storing dates from the past, this is enough information to do any necessary arithmetic. It uses the walrus operator to assign the return value of time_amount() to t and includes t only if it is True. Taking 1st April 2012 as an example. 这篇文章主要介绍了Python之日期与时间处理模块(date和datetime),小编觉得挺不错的,现在分享给大家,也给大家做个参考。一起跟随小编过来看看吧 asked Aug 9 '11 at 16:43. Here are a few good places to start: One great example of this irregularity is daylight saving time. This means that January 31, 2020, is written as 31-01-2020. Plus, you’re going to develop a neat application to count down the time remaining until the next PyCon US! In an earlier section, you learned that you shouldn’t use .utcnow() to create a datetime instance at the current UTC. These methods don’t require you to use integers to specify each attribute, but instead allow you to use some other information: These three ways of creating datetime instances are helpful when you don’t know in advance what information you need to pass into the basic initializers. To do any necessary arithmetic as the time starts, and is platform dependent provide a mix of positive negative. To improve your PyCon countdown with time zone information to do any arithmetic! S directive is used for this purpose if you have a time in UTC from which i the. Me ) that is because time.mktime does not take into python datetime to epoch the part... Method because it doesn ’ t make the cut here from the past, this was March 13 2020... 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