11.7. Datetime Timestamp

11.7.1. What is timestamp?

• Seconds since midnight of January 1st, 1970 (1970-01-01 00:00:00 UTC)

• Unix era, also known as "epoch"

• In most systems represented as 32-bit integer

• Max value is 2,147,483,647 (2038-01-19 03:14:07 UTC)

• Min value is -2,147,483,647 (1901-12-13 20:45:52 UTC)

• If you add 1 to max value, you will get overflow to min value

• Linux kernel 5.6 (released 29 March 2020) has a fix for this problem so that 32-bit systems can run beyond the year 2038

• https://itsfoss.com/linux-kernel-5-6/

• https://lore.kernel.org/lkml/CAHk-=wi9ZT7Stg-uSpX0UWQzam6OP9Jzz6Xu1CkYu1cicpD5OA@mail.gmail.com/

• https://en.wikipedia.org/wiki/Year_2038_problem

11.7.2. Get current timestamp

Get current timestamp using datetime module:

>>> from datetime import datetime
>>>
>>>
>>> current_timestamp = datetime.now().timestamp()

Get current timestamp using time module:

>>> import time
>>>
>>>
>>> current_timestamp = time.time()

11.7.3. Convert timestamp to datetime

Convert timestamp to datetime:

>>> from datetime import datetime
>>>
>>>
>>> datetime.fromtimestamp(267809220)  
datetime.datetime(1978, 6, 27, 17, 27)

• JavaScript has timestamp in milliseconds

• To convert from milliseconds we have to divide by 1000

Convert JavaScript timestamp to datetime:

>>> from datetime import datetime
>>>
>>> MILLISECONDS = 1000
>>>
>>> datetime.fromtimestamp(267809220000 / MILLISECONDS)  
datetime.datetime(1978, 6, 27, 17, 27)

11.7.4. Assignments

Code 11.39. Solution

"""
* Assignment: Datetime Timestamp Limits
* Complexity: easy
* Lines of code: 1 lines
* Time: 5 min

English:
    1. Convert given dates to `datetime` objects
    2. Print timestamp for each date
    3. What is special about those dates?
    4. Run doctests - all must succeed

Polish:
    1. Przekonwertuj podane daty do obiektów `datetime`
    2. Wypisz timestamp każdej daty
    3. Co to za daty?
    4. Uruchom doctesty - wszystkie muszą się powieść

Tests:
    >>> import sys; sys.tracebacklimit = 0

    >>> assert type(a) is float, \
    '`a` must be a float object'

    >>> assert type(b) is float, \
    '`b` must be a float object'

    >>> assert type(c) is float, \
    '`c` must be a float object'

    >>> a
    -2115947647.0
    >>> b
    0.0
    >>> c
    2147483647.0
"""

from datetime import datetime


A = '1902-12-13T20:45:53+00:00'
B = '1970-01-01T00:00:00+00:00'
C = '2038-01-19T03:14:07+00:00'

# timestamp of A
# type: float
a = ...

# timestamp of B
# type: float
b = ...

# timestamp of C
# type: float
c = ...