Find out how long a build took

Is it possible to find out how long a build took? nix log $(which bash) has the build log but no timing information.

Nom (GitHub - maralorn/nix-output-monitor: Pipe your nix-build output through the nix-output-monitor a.k.a nom to get additional information while building.) could help you. It tracks how long a rebuild, shell or build command took.