TUI calendar for the Serbian Orthodox Church, ported from the original DOS Turbo Pascal 6/7 program to Free Pascal (FPC) for Linux, Windows, and macOS.
Original authors: Ivona Maric, Nikola Lecic, Nikola Reljin
Original release: 1993
Original source: Turbo Pascal 6/7, DOS, ~1260 lines
This port: Free Pascal 3.x, cross-platform TUI (crt unit)
PravKal is a TUI (terminal) Orthodox calendar for the Serbian Orthodox Church. It displays parallel Gregorian and Julian dates, fixed and movable feasts, fasting days, and the Byzantine year. It is a port of the original DOS program written in Turbo Pascal — adapted for modern systems (Linux, Windows, macOS) using the Free Pascal compiler.
PravKal је текстуални (TUI) православни календар за Српску Православну Цркву. Приказује паралелне григоријанске и јулијанске датуме, покретне и непокретне празнике, дане поста и византијску годину. Програм је порт оригиналног DOS програма написаног у Turbo Pascal-у — прилагођен за рад на савременим системима (Linux, Windows, macOS) уз помоћ Free Pascal компилатора.
v1.0.0: Кориснички интерфејс је у потпуности на српској ћирилици, а ивице прозора користе праве линијске знакове (Unicode box-drawing). Захтева UTF-8 терминал. / The interface is fully in Serbian Cyrillic and window borders use real Unicode box-drawing glyphs; a UTF-8 terminal is required.
| English | Српски |
|---|---|
| Monthly calendar view with Julian dates | Приказ месечног календара са јулијанским датумима |
| Paschalion: Easter date computed over 532-year cycle | Пасхалион: израчунавање датума Васкрса по 532-годишњем циклусу |
Fasting-day markers (*) |
Означавање дана поста (*) |
| Export month and fasting schedule to TXT (F7 / F8) | Извоз месечног календара и табеле постова у TXT фајл (F7 / F8) |
| Heortology: feast-day texts (F5) | Хеортологија: текстови за велике празнике (F5) |
| Byzantine year and Indiction | Византијска година и индикт |
Main calendar view — parallel Gregorian (G) and Julian (J) columns, feast-day
colours (yellow = major, cyan = Sunday/movable), red ■ fasting markers, Byzantine
year and Indiction in the right panel.
Month scroll — ↑/↓ arrows scroll the week window within the month.
Date navigation (F3) — change month with PgUp/PgDn, year with +/−.
Heortology viewer (F5) — lists available feast-day texts from .KAL files.
Drop-down menu (F10) — Опције (Options) submenu showing all calendar functions.
January view — Jan 7 = Christmas (Божић, Julian Dec 25), Jan 6 = Christmas Eve
(Бадњи дан). Red ■ fasting markers on days 1–6 (Nativity Fast).
- Parallel Gregorian / Julian date columns (SOC uses Julian calendar)
- 532-year Alexandrian Paschalion computed at runtime via Meeus algorithm
- Movable feast names derived from Easter (Pascha), fixed feasts from data tables
- Fasting-day markers on each calendar row
- Byzantine year and liturgical Indiction display
- Month/year navigation, print-to-stdout, heortology viewer
- Pure TUI — runs in any 80×25 terminal (xterm, gnome-terminal, Windows Terminal)
| Tool | Version |
|---|---|
| Free Pascal Compiler | 3.2.x or later |
| Terminal | 80 columns × 25 rows minimum |
Install FPC on Ubuntu/Debian:
sudo apt install fpc
bash build.shThis compiles src/pravkal.pas into ./pravkal and copies the runtime
.KAL / .MOL data files from data/ to the project root (where the binary
expects them).
The obj/ directory holds intermediate FPC unit files and is created
automatically on first build.
cd /path/to/PravKal
./pravkalOptions:
| Flag | Description |
|---|---|
-h, --help |
Print usage and exit |
-v, --version |
Print version and exit |
The program must be launched from the directory that contains the binary
(so that data-file lookups via ExtractFilePath(ParamStr(0)) resolve correctly).
| Key | Action |
|---|---|
| ↑ / ↓ | Scroll weeks within current month |
| F3 | Change month / year dialog |
| F5 | Heortology viewer (feast-day texts from .KAL files) |
| F7 | Export current month to TXT (mesec_YYYY_MM.txt) |
| F8 | Export fasting schedule to TXT (postovi_YYYY.txt) |
| F10 | Drop-down menu |
| Ctrl-C | Exit |
Inside the F3 date dialog:
| Key | Action |
|---|---|
| PgUp / PgDn | Next / previous month |
| + / − | Increment / decrement year |
| Enter | Confirm |
| Esc | Cancel |
All runtime data lives in data/ (committed) and is copied to the project
root by build.sh at build time.
| File | Content |
|---|---|
_PRAZ1.KAL |
Heortology text: Blagovesti (Annunciation) |
_PRAZ2.KAL |
Heortology text: Krstovdan (Elevation of the Cross) |
_PRAZ3.KAL |
Heortology text: Nativity of the Theotokos |
_PRAZ4.KAL |
Heortology text: Presentation of the Theotokos |
_PRAZ5.KAL |
Heortology text: Bozic (Christmas / Nativity of Christ) |
_PRAZ6.KAL |
Heortology text: Bozic (alternate text) |
_GRESKE.MOL |
Exit-screen text (prayer / closing message) |
_KRST.GEI |
Original DOS cross graphic (not used in FPC port) |
PravKal/
├── build.sh # Build + data-copy script
├── data/ # Canonical runtime data files
├── obj/ # FPC intermediate files (generated, gitignored)
├── src/
│ ├── pravkal.pas # Main program
│ ├── kalsys1.pas # Calendar engine (Paschalion, leap year, colours)
│ ├── kalmenu1.pas # Menu bar, drop-downs, function-key strip
│ ├── kalwork1.pas # Screen I/O, dialogs, key handling
│ └── nizz.pas # String utilities, shared types
└── README.md
- Calendar display: month view, D/G/J columns, fasting markers
- Paschalion: 532-year cycle computed at runtime, correct for any year
- Julian date conversion: 13-day offset, century-year adjustments
- Navigation: ↑/↓ scroll within month, F3 change date
- Movable feasts: Pascha, Holy Week, Pentecost, all derived feasts
- Heortology viewer: F5 opens .KAL texts
- Export month to TXT: F7 →
mesec_YYYY_MM.txt - Export fasting schedule to TXT: F8 →
postovi_YYYY.txt - About dialog: F10 → Desk → Program...
- Fasting table: F10 → Opcije → Postovi
- Indiction table: F10 → Opcije → Indiktion
- Exit: Ctrl-C
- Search (Traganje menu): all four search items (date, feast, fast, Sunday) are wired in the menu but have no implementation — stubs only
- Configuration (Konfiguracija): menu item present, no implementation
- Save configuration: menu item present, no implementation
- Help (F1): shows in strip, no dialog implemented
- Contents (Alt-F1): no implementation
- Scrolling animation within month:
premwindsveis a no-op stub; month view redraws fully on scroll (no smooth line-by-line scroll as in original DOS version) - Box-drawing characters: now uses Unicode single-line box-drawing glyphs (
┌ ─ ┐ │ └ ┘ ├ ┤ ┬ ┴ ┼) with correct grid junctions (since v1.0.0) - Multi-byte search input editing: typing/back-spacing Cyrillic in the feast-search box edits by UTF-8 byte, not by glyph (cosmetic; matching still works)
The SOC uses the Julian calendar for all liturgical dates. The program displays both Gregorian (column G) and Julian (column J) dates side by side. In 2026 the offset is 13 days (Julian is 13 days behind Gregorian).
Paschalion anchor: year 1941 (start of the current 532-year Great Indiction cycle). Julian Easter 1941 = April 7 Julian = April 20 Gregorian. ✓
Byzantine year (shown in info panel): approximately Gregorian year + 5508, adjusted September for the ecclesiastical New Year.
PravKal is the original DOS-era Serbian calendar, preserved and ported for modern terminals. For a full-featured, multi-tradition web application that continues this work, see:
Orthodox and Oriental Orthodox saints, name-days, liturgical readings, moon phases, and ICS feeds — FastAPI · React · 17 traditions · GitHub Pages
The orthodox-calendar project is the modern successor: it covers 17 Orthodox
and Oriental Orthodox traditions (Serbian, Greek, Russian, Coptic, Ethiopian,
Armenian, …), exposes a REST API, generates iCal feeds, and includes a React
frontend deployed to GitHub Pages. The calendar engine concepts in PravKal —
the Alexandrian Paschalion, Julian date conversion, movable feast offsets —
are all present in expanded form there.
| PravKal | orthodox-calendar | |
|---|---|---|
| Interface | TUI (80×25 terminal) | Web (React + FastAPI) |
| Traditions | Serbian Orthodox Church | 17 traditions |
| Language | Free Pascal | Python + TypeScript |
| Output | Terminal / TXT export | Browser / REST API / ICS |
| Paschalion | ✓ (Meeus algorithm) | ✓ (expanded) |
| Hagiography | Limited (6 .KAL texts) | 1100+ saints |
- Lazarus GUI port: reuse
kalsys1.pascalendar engine; wrap in LCL (Lazarus Component Library) for native GUI on Linux, Windows, macOS - Larger screen support: parameterise
SCREEN_W/SCREEN_H, remove 80×25 hardcoding - Hagiography: integrate Serbian Prologue (Prolog iz Ohrida) content
for feast-day texts in
.KALfiles - Extended date range: current algorithm handles 0 AD – 4000 AD correctly via Meeus Julian Easter formula; UI date entry validation to be extended
- Search implementation: Traganje menu — find by date, feast, fast, Sunday
Updated daily. Total and unique cloners over the last 14 days.