Add YEAR function description

docs/src/functions/date-and-time.md

@@ -34,5 +34,5 @@ You can track the progress in this [GitHub issue](https://github.com/ironcalc/Ir
 | WEEKNUM          | <Badge type="info" text="Not implemented yet" /> | –             |
 | WORKDAY          | <Badge type="info" text="Not implemented yet" /> | –             |
 | WORKDAY.INTL     | <Badge type="info" text="Not implemented yet" /> | –             |
-| YEAR             | <Badge type="tip" text="Available" />          | –             |
+| YEAR             | <Badge type="tip" text="Available" />          | [YEAR](date_and_time/year) |
 | YEARFRAC         | <Badge type="info" text="Not implemented yet" /> | –             |

docs/src/functions/date_and_time/year.md

@@ -3,9 +3,35 @@ layout: doc
 outline: deep
 lang: en-US
 ---
-
-# YEAR
-
+# YEAR function
 ::: warning
-🚧 This function is implemented but currently lacks detailed documentation. For guidance, you may refer to the equivalent functionality in [Microsoft Excel documentation](https://support.microsoft.com/en-us/office/excel-functions-by-category-5f91f4e9-7b42-46d2-9bd1-63f26a86c0eb).
-:::
+**Note:** This draft page is under construction 🚧
+:::
+## Overview
+YEAR is a function of the Date and Time category that extracts the year from a valid date [serial number](/features/serial-numbers.md), returning a number in the range [1899, 9999].
+## Usage
+### Syntax
+**YEAR(<span title="Number" style="color:#1E88E5">date</span>) => <span title="Number" style="color:#1E88E5">year</span>**
+### Argument descriptions
+* *date* ([number](/features/value-types#numbers), required). The date for which the year is to be calculated, expressed as a [serial number](/features/serial-numbers.md) in the range [1, 2958466). The value 1 corresponds to the date 1899-12-31, while 2958465 corresponds to 9999-12-31.
+### Additional guidance
+If the supplied _date_ argument has a fractional part, YEAR uses its [floor value](https://en.wikipedia.org/wiki/Floor_and_ceiling_functions).
+### Returned value
+YEAR returns an integer [number](/features/value-types#numbers) in the range [1899, 9999], that is the year according to the [Gregorian calendar](https://en.wikipedia.org/wiki/Gregorian_calendar).
+### Error conditions
+* In common with many other IronCalc functions, YEAR propagates errors that are found in its argument.
+* If no argument, or more than one argument, is supplied, then YEAR returns the [`#ERROR!`](/features/error-types.md#error) error.
+* If the value of the *date* argument is not (or cannot be converted to) a [number](/features/value-types#numbers), then YEAR returns the [`#VALUE!`](/features/error-types.md#value) error.
+* For some argument values, YEAR may return the [`#DIV/0!`](/features/error-types.md#div-0) error.
+* If date is less than 0, or greater than or equal to 2,958,466, then YEAR returns the [`#NUM!`](/features/error-types.md#num) error.
+* At present, YEAR does not accept a string representation of a date literal as an argument. For example, the formula `=YEAR("2024-12-31")` returns the [`#VALUE!`](/features/error-types.md#value) error.
+<!--@include: ../markdown-snippets/error-type-details.txt-->
+## Details
+IronCalc utilizes Rust's [chrono](https://docs.rs/chrono/latest/chrono/) crate to implement the YEAR function.
+## Examples
+[See some examples in IronCalc](https://app.ironcalc.com/?example=year).
+
+## Links
+* See also IronCalc's [DAY](/functions/date_and_time/day.md) and [MONTH](/functions/date_and_time/month.md) functions.
+* Visit Microsoft Excel's [YEAR function](https://support.microsoft.com/en-gb/office/year-function-c64f017a-1354-490d-981f-578e8ec8d3b9) page.
+* Both [Google Sheets](https://support.google.com/docs/answer/3093061) and [LibreOffice Calc](https://wiki.documentfoundation.org/Documentation/Calc_Functions/YEAR) provide versions of the YEAR function.