# Cronslab
An advanced redstone scheduler block with a similar syntax to [cron](https://en.wikipedia.org/wiki/Cron). See [#usage](#usage "mention") for a heavily detailed overview, or [Examples](/cronslab/examples.md) for a quick start.
### Crafting
### Usage
Right click to open the GUI and input the expression. The GUI contains a "to English" translator of the given expression, but this is also gone over below.
#### Fields
A cronslab is made up of four fields representing **ticks**, **seconds**, **minutes**, and **minecraft days**. Each describes which value of that field's interval the signal should be active.
{% hint style="info" %}
There are some extra rules for this different to cron, but have been made in a way that tries to 'make sense' for Minecraft, and doesn't need consideration. See [#quirks](#quirks "mention").
{% endhint %}
Example:
The **tick** field has an interval of **20** (since 20 ticks = 1 second). So for the following values of the field:
```
0: The 0th tick of every second.
*: Every tick of every second.
*/4: The 4th tick.
0-3: 0th to 3rd tick.
0-9/2: Every even tick between 0 and 9.
```
Fields can be a comma-separated list of values, which pass if any value passes (an OR expression):
```
5,6: The 5th or 6th tick of.
*/2,15: Any even tick, or the 15th tick.
```
#### Expression
An expression is made of the four fields, where all must pass to emit a signal.
```
* 0-29 */2 *: Constant for the first 30 seconds of the minute AND only every other minute.
0 0-5 * *: Five 1-tick pulses a second apart every minute.
```
### Quirks
There are two things that are worth noting for advanced use.
#### Gametime vs Daytime
Per the [minecraft wiki](https://minecraft.wiki/w/Commands/time#Usage):
> There are \[multiple] types of time:
>
> * Gametime - The total number of [game ticks](https://minecraft.wiki/w/Game_tick) that have elapsed in the world.
> * Daylight cycle time (aka. internal daytime) - The total number of game ticks that have elapsed during the daylight cycle. It does not elapse when the game rule [`advance_time`](https://minecraft.wiki/w/Game_rule#advance_time) is `false`.
By default, the expression evaluator will operate on **gametime**. This counts from the world start, and isn't affected by the `advance_time` gamerule, but might not be synced to the visual day/night cycle. However, if the **day** field is **relevant** (i.e. not `*`), then the Cronslab will work on the **daytime**. This is synchronised with the visual day/night cycle, but will not update when `advance_time` is false.
#### Interval Extension
In normal cron you can't schedule, for example, every 45 minutes in a single expression. Cronslab gets around this by possibly *extending the interval* of a field when checked. The rules are meant be common sense, but for clarify:
* If the field is **cyclical** (a wildcard or unbounded range e.g. `4/2`), then it's interval is multiplied by each field 'ahead' that has at least one **wildcard** value.
* Example: The ticks field in `*/15 * 0 *` will have it's interval extended to `20 * 60 = 1200`, which correctly spaces signals every 15 ticks.
* The **days** field has an effective infinite interval.
---
# Agent Instructions: Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.
Perform an HTTP GET request on the current page URL with the `ask` query parameter:
```
GET https://docs.jackf.red/cronslab/cronslab.md?ask=
```
The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.
Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.