docs: datetime routines

packages/noco-docs/docs/070.fields/040.field-types/060.formula/040.date-functions.md

@@ -94,6 +94,62 @@ Returns the day of the week as an integer between 0 and 6 (inclusive), with Mond
 
 ---
 
+## DATESTR
+The DATESTR function converts a date or datetime field into a string in "YYYY-MM-DD" format.
+
+#### Syntax
+```plaintext
+DATESTR(date | datetime)
+```
+
+#### Sample
+```plaintext
+DATESTR('2022-03-14') => 2022-03-14
+DATESTR('2022-03-14 12:00:00') => 2022-03-14
+``` 
+
+#### Remark
+This function converts a date or datetime field into a string in "YYYY-MM-DD" format, ignoring the time part.
+
+---
+
+## DAY
+The DAY function returns the day of the month as an integer.
+
+#### Syntax
+```plaintext
+DAY(date | datetime)
+```
+
+#### Sample
+```plaintext
+DAY('2022-03-14') => 14
+DAY('2022-03-14 12:00:00') => 14
+```
+
+#### Remark
+This function returns the day of the month as an integer between 1 and 31 (inclusive).
+
+---
+
+## MONTH
+The MONTH function returns the month of the year as an integer.
+
+#### Syntax
+```plaintext
+MONTH(date | datetime)
+```
+
+#### Sample
+```plaintext
+MONTH('2022-03-14') => 3
+MONTH('2022-03-14 12:00:00') => 3
+```
+
+#### Remark
+This function returns the month of the year as an integer between 1 and 12 (inclusive).
+
+---
 
 ## Related Articles
 - [Numeric and Logical Operators](015.operators.md)