---
url: >-
  /statelake/scripting-reference/functions-and-procedures/datetime-functions/isvaliddateday.md
---

# IsValidDateDay

**IsValidDateDay** returns **True** if the given year and day of the year represent components of a valid date.

* **AYear** must be within the range of 1 through 9999 inclusive.
* **ADayOfYear** must fall within the range of 1 through to 366 - depending on the total number of days in **AYear** - whether it is a leap year or not.

January 1st is considered to be day 1, January 2nd is day 2 e.t.c.

Declaration: Function IsValidDateDay(const AYear, ADayOfYear: Word): Boolean;

An example of its use follows.

```pascal
procedure OnMapEvent(var Value:Variant);
var
  TheYear, TheDay : word;
begin
 //Returns true if the given YEAR and DAY are valid date components

 //VALID parts
  TheDay := 290;
  TheYear := 2023;
 If IsValidDateDay(TheYear, TheDay) then
    Loginfo('YAHOO!!! The Day date is valid.')
 else
    LogInfo('OOPS!! The Day date is not valid.');

 //INVALID parts . ... there are not 400 days in a year!
  TheDay := 400;
  TheYear := 2023;
 If IsValidDateDay(TheYear, TheDay) then
    Loginfo('YAHOO!!! The Day date is valid.')
 else
    LogInfo('OOPS!! The Day date is not valid.');

  LogInfo('');
end;
```