I'm the author of Bttf. I just wanted to share a really cool example of something that Bttf can do that I _think_ is kinda hard to do otherwise. (And also, I want to make an assertion about it and I hope this will lead to me being wrong and learning something new.)

The use case is: "I want to see a list of all files in a repository, sorted in ascending order of when it was most recently changed according to source control. I also want to highlight the time with color, make it be in local time and format it in my own bespoke way using strftime." Here's the full command (run from the root of https://github.com/BurntSushi/ripgrep):

    $ git ls-files |
        bttf tag exec git log -n1 --format='%aI' |
        bttf time in system |
        bttf time sort |
        bttf time fmt -f '%a %Y-%m-%d %H:%M:%S' |
        bttf untag -f '{tag}|t{data}'
    ...
    Thu 2025-10-30 13:30:14 crates/ignore/Cargo.toml
    Sat 2025-11-29 14:11:38 crates/core/flags/lowargs.rs
    Wed 2025-12-17 11:38:12 tests/misc.rs
    Wed 2025-12-17 11:38:12 tests/util.rs
    Thu 2026-02-12 20:39:46 crates/ignore/src/default_types.rs
    Fri 2026-02-20 16:06:29 crates/core/flags/config.rs
    Fri 2026-02-27 11:25:19 GUIDE.md
    Fri 2026-02-27 11:25:19 crates/core/flags/defs.rs
    Mon 2026-05-25 23:56:53 CONTRIBUTING.md
    Tue 2026-05-26 08:32:43 AI_POLICY.md

Or even ask for a specific time window:

    $ git ls-files |
        bttf tag exec git log -n1 --format='%aI' |
        bttf time in system |
        bttf time cmp ge 2026-01-01 |
        bttf time cmp lt 2026-04-01 |
        bttf time sort |
        bttf time fmt -f '%a %Y-%m-%d %H:%M:%S' |
        bttf untag -f '{tag}|t{data}'
    Thu 2026-02-12 20:39:46 crates/ignore/src/default_types.rs
    Fri 2026-02-20 16:06:29 crates/core/flags/config.rs
    Fri 2026-02-27 11:25:19 GUIDE.md
    Fri 2026-02-27 11:25:19 crates/core/flags/defs.rs

If you run this on a big repository, it will take quite a lot of time because `git log -n1` takes a long time. I think this is the fastest way to get the most recent commit time on a single file? (That's the assertion that I hope someone can correct me on!) In any case, `bttf tag exec` is using parallelism under the hood to make this even faster.

Bttf is a command line datetime Swiss army knife