From OSTree's Release 2016.6 change log:

"Use OSTREE_TIMESTAMP (=1) for checked-out files

Is a quite interesting change - we previously used a
timestamp of zero, but Nix has apparently done better
with 1 for various reasons. This is a pretty subtle
change, so be on the lookout for regressions."

Change-Id: I8349fc52604603faef1c39bf88ba0e6591ae92a1
Reviewed-by: Samuli Piippo <samuli.piippo@qt.io>