Date

A Date field, variable or expression can be in the range of 1/1/100 to 12/31/32,767.

Although the representation mode for dates by can work with dates up to the year 32 767, certain operations passing through the system impose a lower limit.

Note: In the 4D Language Reference manual, Date parameters in command descriptions are denoted as Date, except when marked otherwise.

Date literals

A date literal constant is enclosed by exclamation marks (!…!). A date must be structured using the ISO format (!YYYY-MM-DD!). Here are some examples of date constants:

!1976-01-01!
!2004-09-29!
!2015-12-31!

A null date is specified by !00-00-00!.

Tip: The Code Editor includes a shortcut for entering a null date. To type a null date, enter the exclamation (!) character and press Enter.

Notes:

• For compatibility reasons, 4D accepts date inputs using system format with two-digit years, such as !12/04/98!. A two-digit year is assumed to be in the 20th or 21st century based on whether it is greater or less than 30, unless this default setting has been changed using the SET DEFAULT CENTURY command.
• If you have checked the "Use regional system settings" option (see Methods Page), you must use the date format defined in your system. Generally, in a US environment, dates are entered in the form month/day/year, with a slash "/" separating the values.

Date operators

Operation	Syntax	Returns	Expression	Value
Date difference	Date – Date	Number	!2017-01-20! - !2017-01-01!	19
Day addition	Date + Number	Date	!2017-01-20! + 9	!2017-01-29!
Day subtraction	Date – Number	Date	!2017-01-20! - 9	!2017-01-11!
Equality	Date = Date	Boolean	!2017-01-01! =!2017-01-01!	True
			!2017-01-20! = !2017-01-01!	False
Inequality	Date # Date	Boolean	!2017-01-20! # !2017-01-01!	True
			!2017-01-20! # !2017-01-20!	False
Greater than	Date > Date	Boolean	!2017-01-20! > !2017-01-01!	True
			!2017-01-20! > !2017-01-20!	False
Less than	Date < Date	Boolean	!2017-01-01! < !2017-01-20!	True
			!2017-01-20! < !2017-01-20!	False
Greater than or equal to	Date >= Date	Boolean	!2017-01-20! >=!2017-01-01!	True
			!2017-01-01!>=!2017-01-20!	False
Less than or equal to	Date <= Date	Boolean	!2017-01-01! <= !2017-01-20!	True
			!2017-01-20! <= !2017-01-01!	False

Conversion of dates from JavaScript

Since dates in JavaScript are objects, they are sent to 4D as text containing their JSON form like any other object. This principle is implemented in particular when using JSON commands or Web Areas.

The JSON form of JavaScript Date objects follows the ISO 8601 standard, for example "2013-08-23T00:00:00Z". It is your responsibility to convert this text into a 4D date. Two solutions are available:

Using the JSON Parse command:

 var $dateIso : Text // reception of a date in ISO format
 var $date4D : Date 
 $date4D:=JSON Parse("\""+$dateIso+"\"";Is date))

Using the Date command:

 var $dateIso : Text // reception of a date in ISO format
 var $date4D : Date 
 $date4D:=Date($dateIso)

Note the difference between these two solutions: JSON Parse respects the conversion mode set using the SET DATABASE PARAMETER (if any), while Date is not subject to this. Conversion using the Date command always takes the local time zone into account.

note

When the current date storage setting is date type (default), JSON date strings in "YYYY-MM-DD" format are automatically handled as date values by the JSON Parse and Date commands.