Convert Unix timestamp value to human readable python

Question

I have a Unix timestamp which value is 1502878840. This Unix timestamp value can be converted to human readable like Aug 16, 2017 10:20:40. I have 2 following python code to convert 1502878840 to Aug 16, 2017 10:20:40. Both of them give a same result (Aug 16, 2017 10:20:40)

First method
utc = datetime.fromtimestamp(1502878840)
Second method
utc = datetime(1970, 1, 1) + timedelta(seconds=1502878840)

Could anyone answer me 2 following questions.
1. The result of 2 methods are same. But at the logic view point of Python code, is there any case that may cause the difference in result?
I ask this question because I see most of the python code use First method.
2. As I read here, the Unix time will have a problem on 19 January, 2038 03:14:08 GMT.
I run a timestamp which has a date after 19.Jan, 2038 (2148632440- Feb 01, 2038 10:20:40). The result is as follows
First method: ValueError: timestamp out of range for platform time_t
Second method: 2038-02-01 10:20:40
Question is: Can I use Second method to overcome the problem of "Year 2038 problem"?

@Mark Tolonen: Thank you so much for your suggestion. I read manual of datetime again. It is better if we use utcfromtimestamp — jackbk
– jackbk, Commented Aug 18, 2017 at 2:34

Laurent LAPORTE · Accepted Answer · 2017-08-16 06:01:33Z

3

Quoting the documentation:

fromtimestamp() may raise OverflowError, if the timestamp is out of the range of values supported by the platform C localtime() or gmtime() functions, and OSError on localtime() or gmtime() failure. It’s common for this to be restricted to years in 1970 through 2038. Note that on non-POSIX systems that include leap seconds in their notion of a timestamp, leap seconds are ignored by fromtimestamp(), and then it’s possible to have two timestamps differing by a second that yield identical datetime objects. See also utcfromtimestamp().

The second solution solves your problem:

utc = datetime(1970, 1, 1) + timedelta(seconds=1502878840)

answered Aug 16, 2017 at 6:01

Laurent LAPORTE

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4 Comments

Gribouillis Over a year ago

The timedelta documentation mentions a limit of 999999999 days. That's less than 3M years. The planet earth may last much longer than that.

Laurent LAPORTE Over a year ago

@Gribouillis Good news, and Python may survive to that 🙂

jackbk Over a year ago

@Laurent LAPORTE : Thank you for your answer. By this answer, I have a method to overcome the Year 2038 problem.

jackbk Over a year ago

@Gribouillis: Thank you for your information. Actually, my intention is to solve Year 2038 problem firstly. I know that timedelta has a limitation as your mention (3M years), but for a very far future like that, we can not sure anything. The hardware running python program can running until to the next 3M years? I see some RTC chip also limits their correct operation until 2099 :).

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