The Advent Progress Tally Protocol (APT.Pt for short) defines a system to communicate the progress of the season of Advent in Christian churches asynchrounously.

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.

The time between the first and the 25th day of the last month in the Gregorian Calendar

Any binary display which can be toggled at least by a person physically present. It can, but does not have to be, a typical wax candle.

A traditional APT4 device, comprised of an (often wooden) ring decorated with pine branches and other fitting objects, and 4 Candles placed on top.

A traditional APT24 device, comprised of 24 closed compartments containing small gifts.

One of the last four Sundays before the last day of Advent. Sundays in Advent are indexed chronologically, starting with 1 on the first Sunday. The 1st Advent Sunday MAY be in the second last month, and the 4th Advent Sunday MAY be on the 24th day of Advent.

There are many methods to display progress through a time period. One of these is the traditional practice of Advent Calendars and Advent Wreathes, said to be invented by the theologist Johann Hinrich Wichern in 1839 (Source: Wikipedia). This document seeks to standardize these devices, and preserve their idea for the future.

All APT.Pt devices SHOULD be updated regularly, and removed soon after Christmas. Please respect local waste disposal regulations and recommendations, especially regarding electronics and candles.

An APT4 device consists of four Candles arranged in close enough proximity to be observed at the same time. If the device is active, candles are activated to match the amount of Advent Sundays passed, including the current day (see Appendix A). If the device is active, and a used Candle's Off state differs from that of an unused candle, there SHOULD NOT be any inactive used candles. If Candles have a limited supply of a consumant, such as fuel, wax or charge, they SHOULD be exchanged in time before fully exhausting it.

An APT4 device MAY be shared between multiple users. Users MAY agree on a pattern ensuring equal usage distribution between them.

Historically, Advent Wreathes containing 18 to 24 small Candles and 4 big Candles have been produced. In this case, one small Candle is lit for every day passed as on APT24, and big Candles are lit in the same patterns as on APT4 devices.

The design of an APT24 device is more free. The only constraints are that at the beginning of the advent, there SHOULD be 24 numbered containers, which in present implementations often contain chocolate or other small gifts. The 24th container is often implemented containing a gift which is larger and/or slightly more valuable. Every day, the user SHOULD open the compartment labelled with the current date, and recieve the gift inside. In some implementations, the container MAY be removed afterwards, and is sometimes part of the gift. This choice is up to the implementation. The user MUST NOT open compartments designated for future dates. If, due to a planned or unplanned incident, a compartment is not opened on it's designated date, it SHOULD be opened at any date in the future. Implementations may choose if correct order of opening is required.

An APT24 device SHOULD NOT be shared between multiple users. In edge cases, after an advance agreement, users MAY share a device. In this case, gifts should be distributed so that all users recieve approximatly equally valued items, both in monetary and emotional value and usefulness.

Before disposing of an APT24 device, the user SHOULD ensure that no gifts have remained in the device.

As an example, this table shows the number of Candles lit on specific dates in 2025.

Bejamin Morgenstern, for inspiring me to write this, by writing SAWP (unpublished), and proofreading. Michelle Warnatz, for more proofreading.

This is version 1.0 of the document.

It has been created by Linus Warnatz on 2024-12-15.

Please append a version history here once there are multiple versions.