tcm-organ-clock

TCM organ clock anchored on the solar day -- tray icon, table and dial.

The model

Every clock here is anchored on geometric sunrise — the instant the Sun's upper limb crosses the true horizon (θ = −0.267°). Not refracted sunrise, not civil twilight, not a fixed clock hour. The reasoning: twilight brightness is a smooth curve, so every depression angle someone might pick is a convention; a geometric crossing is not.

Consequences worth knowing before you compare it to other software:

• The day and night arcs are elastic. They stretch and shrink with the season, so a "period" is not a fixed number of minutes.
• Outside roughly ±66.6° latitude the model is undefined — the sun does not both rise and set — and the app says so rather than inventing times.
• Times will not match published tables that use clock hours.

Install and run

Python 3.11+.

pip install -r requirements.txt
python tcm_organ_clock.py

Nothing else to install: the model package ships inside this repository.

The app starts on Bucharest. Change it from the export dialog ("Set as Default"); the choice is saved and survives restarts.

Licence

GPL-3.0-or-later. Copyright (C) 2026 Perieteanu Costin.

This program links PyQt6, which is GPL or commercial — hence GPL here.

Credits

Developed by Perieteanu Costin in collaboration with Claude (Anthropic's Claude Code).