Morrow.mojo

Human-friendly date and time utilities for Mojo. Morrow provides an Arrow-inspired API for creating, parsing, formatting, shifting, comparing, and humanizing date-time values.

Language: English | 中文

Documentation: https://mojoto.github.io/morrow.mojo/

Installation

Add the Modular and Modular Community channels to your Pixi workspace, then install Morrow:

pixi workspace channel add --prepend https://repo.prefix.dev/modular-community
pixi workspace channel add --prepend https://repo.prefix.dev/max
pixi add morrow

The package installs a compiler-compatible morrow.mojoc into the active Pixi environment, so it can be imported without copying source files.

To work from a source checkout, install uv and run:

make install

make install creates or reuses .venv with Python 3.14, installs the pinned Mojo version, and prints it. All Mojo targets in the Makefile run through uv run mojo.

Start the Mojo REPL from the project root to use the source package directly:

uv run mojo repl

Usage

Paste the following example into the REPL:

from morrow import FORMAT_RSS, Morrow, TimeZone

var now = Morrow.now()
print(now)

var utc = Morrow.utcnow()
print(utc)

var parsed = Morrow.get("2026-01-01 03:04:05Z")
print(parsed)
print(parsed.format("YYYY-MM-DD HH:mm:ss ZZ"))

var beijing = parsed.to("+08:00")
print(beijing)

var hour = beijing.span("hour")
print(hour)

print(beijing.isocalendar())
print(beijing.timetuple())

var rss = Morrow(2026, 1, 1, 10, 30, 35, 0, TimeZone(0, "UTC"))
print(rss.format(FORMAT_RSS))

Morrow is UTC by default, supports fixed-offset time zones, parses ISO 8601 strings and POSIX timestamps, and formats values with Arrow-style tokens or Python-style strftime.

Using Morrow in another project

Copy the morrow source directory into your project, or build a precompiled package:

make build

This creates morrow.mojoc. Precompiled Mojo packages are tied to the compiler version that created them, so use the same Mojo version when importing one. Matching artifacts may also be available from releases.

Development

Run make help to list the available targets.

Target	Description
make install	Create or reuse .venv and install Mojo with uv (prereleases allowed)
make test	Run every tests/test_*.mojo file
make format	Format the morrow and tests directories
make build	Precompile morrow as morrow.mojoc
make package	Build the distributable Conda package with rattler-build
make clean	Remove morrow.mojoc
make doc-install	Install Docusaurus dependencies
make doc-build	Build the Docusaurus static site
make doc-serve	Serve the built Docusaurus site
make doc-clean	Remove generated Docusaurus files

The documentation targets require Node.js and npm. Run make doc-install before building the documentation, then use make doc-build followed by make doc-serve to preview the built site.