Show HN: Calgebra – Set algebra for calendars in Python (github.com)

calgebra lets you compose calendar timelines using Python's set operators: | (union), & (intersection), - (difference), and ~ (complement).

Queries are lazy—you build expressions first, then execute via slicing.

Example – find when a team is free for a 2+ hour meeting:

  from calgebra import day_of_week, time_of_day, hours, HOUR

  # Define business hours
  weekend = day_of_week(["saturday", "sunday"], tz="US/Pacific")
  weekdays = ~weekend
  business_hours = weekdays & time_of_day(start=9*HOUR, duration=8*HOUR, tz="US/Pacific")

  # Team calendars (Google Calendar, .ics files, etc.)
  team_busy = alice | bob | charlie

  # One expression to find available slots
  free_slots = (business_hours - team_busy) & (hours >= 2)

Features:

- Set operations on any timeline source

- Recurring patterns via RFC 5545 (dateutil under the hood)

- Filter by duration, metadata, or custom properties

- Google Calendar read/write

- iCalendar (.ics) import/export

Fwiw, I think focused DSLs are a great pairing with code-focused agents like huggingface's smol-agents or agex (my other hobby project).

Video of a calgebra-enabled agent: https://youtu.be/10kG4tw0D4k

Would love feedback!

Pretty cool! A small but useful library for working with calendar intervals and schedules in Python