On berlin, I see that timestamps on directories are not reset:
--8<---------------cut here---------------start------------->8---
ludo@berlin ~$ find
/gnu/store/yn7dx3jkb18mc7dwnsn2izix2f62riw8-python-tables-3.4.4 -exec stat -c
'%y %n' {} \;
1970-01-01 01:00:01.000000000 +0100
/gnu/store/yn7dx3jkb18mc7dwnsn2izix2f62riw8-python-tables-3.4.4
1970-01-01 01:00:01.000000000 +0100
/gnu/store/yn7dx3jkb18mc7dwnsn2izix2f62riw8-python-tables-3.4.4/lib
1970-01-01 01:00:01.000000000 +0100
/gnu/store/yn7dx3jkb18mc7dwnsn2izix2f62riw8-python-tables-3.4.4/lib/python3.7
1970-01-01 01:00:01.000000000 +0100
/gnu/store/yn7dx3jkb18mc7dwnsn2izix2f62riw8-python-tables-3.4.4/lib/python3.7/site-packages
2018-11-13 00:32:27.631418400 +0100
/gnu/store/yn7dx3jkb18mc7dwnsn2izix2f62riw8-python-tables-3.4.4/lib/python3.7/site-packages/tables-3.4.4-py3.7.egg-info
1970-01-01 01:00:01.000000000 +0100
/gnu/store/yn7dx3jkb18mc7dwnsn2izix2f62riw8-python-tables-3.4.4/lib/python3.7/site-packages/tables-3.4.4-py3.7.egg-info/SOURCES.txt
1970-01-01 01:00:01.000000000 +0100
/gnu/store/yn7dx3jkb18mc7dwnsn2izix2f62riw8-python-tables-3.4.4/lib/python3.7/site-packages/tables-3.4.4-py3.7.egg-info/requires.txt
1970-01-01 01:00:00.000000000 +0100
/gnu/store/yn7dx3jkb18mc7dwnsn2izix2f62riw8-python-tables-3.4.4/lib/python3.7/site-packages/tables-3.4.4-py3.7.egg-info/dependency_links.txt
1970-01-01 01:00:01.000000000 +0100
/gnu/store/yn7dx3jkb18mc7dwnsn2izix2f62riw8-python-tables-3.4.4/lib/python3.7/site-packages/tables-3.4.4-py3.7.egg-info/entry_points.txt
1970-01-01 01:00:00.000000000 +0100
/gnu/store/yn7dx3jkb18mc7dwnsn2izix2f62riw8-python-tables-3.4.4/lib/python3.7/site-packages/tables-3.4.4-py3.7.egg-info/not-zip-safe
1970-01-01 01:00:01.000000000 +0100
/gnu/store/yn7dx3jkb18mc7dwnsn2izix2f62riw8-python-tables-3.4.4/lib/python3.7/site-packages/tables-3.4.4-py3.7.egg-info/top_level.txt
1970-01-01 01:00:01.000000000 +0100
/gnu/store/yn7dx3jkb18mc7dwnsn2izix2f62riw8-python-tables-3.4.4/lib/python3.7/site-packages/tables-3.4.4-py3.7.egg-info/PKG-INFO
2018-11-13 00:32:27.627418400 +0100
/gnu/store/yn7dx3jkb18mc7dwnsn2izix2f62riw8-python-tables-3.4.4/lib/python3.7/site-packages/tables
1970-01-01 01:00:01.000000000 +0100
/gnu/store/yn7dx3jkb18mc7dwnsn2izix2f62riw8-python-tables-3.4.4/lib/python3.7/site-packages/tables/utils.py
1970-01-01 01:00:01.000000000 +0100
/gnu/store/yn7dx3jkb18mc7dwnsn2izix2f62riw8-python-tables-3.4.4/lib/python3.7/site-packages/tables/index.py
2018-11-13 00:32:27.623418400 +0100
/gnu/store/yn7dx3jkb18mc7dwnsn2izix2f62riw8-python-tables-3.4.4/lib/python3.7/site-packages/tables/tests
[...]
--8<---------------cut here---------------end--------------->8---
This is probably a bug in (guix store database) as used by ‘guix
offload’.
Ludo’.
