Bug summary

I have a very curious problem withnum2date which I am not able to understand where it comes from. It seems that when running a code snippet (which is working as expected in a conda environment) within a container on a specific machine with time zone EET,num2date introduces a 2-hour offset from UTC associated to the time zone. The weird fact is that the time seems to be the same for both machines, so I do not understand where such extra two hours is applied. it is interesting also since thedate2num works fine...

Unfortunately this is partially reproducible since this is happening within a singularity container that I cannot share easily. I am wondering if such potential issues with time zones are known to show up inside containers.

It might be a feature that I am not aware but I cannot understand how to control this.

Code for reproduction

fromdatetimeimportdatetime,timezoneimportmatplotlib.datesasmdatesimporttimeprint("Time:",time.strftime("%Y-%m-%d %H:%M:%S",time.localtime()))print("System timezone according to time module:",time.tzname)original=datetime(1989,1,1,tzinfo=timezone.utc)num=mdates.date2num(original)converted=mdates.num2date(num,tz=timezone.utc)print("Epoch:",mdates.get_epoch())print("Original datetime:     ",original)print("Converted to num:      ",num)print("Back to datetime:      ",converted)

Actual outcome

On the container

Time: 2025-06-03 19:30:19System timezone according to time module: ('EET', 'EEST')Epoch: 1970-01-01T00:00:00Original datetime:      1989-01-01 00:00:00+00:00Converted to num:       6940.0Back to datetime:       1988-12-31 22:00:00+00:00

Expected outcome

On the conda envrionment:

Time: 2025-06-03 19:30:23System timezone according to time module: ('EET', 'EEST')Epoch: 1970-01-01T00:00:00Original datetime:      1989-01-01 00:00:00+00:00Converted to num:       6940.0Back to datetime:       1989-01-01 00:00:00+00:00

Additional information

Running matplotlib 3.10.3

Operating system

unix

Matplotlib Version

matplotlib 3.10.3

Matplotlib Backend

agg

Python version

3.12

Jupyter version

No response

Installation

conda