Apptainer and singularity ce are quite common in HPC. While both implementations fork the old singularity project, they are not really identical.
We use singularity in the HPCs (like Leonardo, LUMI, Fugaku, NeSI NZ, Levante) but some devs and researchers have apptainer installed locally.
We found a timezone bug a few days ago in our Python code (matplotlib,xarray,etc.), but that didn't happen with apptainer.
As the code bases are still a bit similar, I could confirm apptainer fixed it but singularity ce was still affected by the bug -- singularity replaces the UTC timezone file by the user's timezone, Helsinki EEST in our case in LUMI HPC.
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