DMN13 — Equality for date, date and time, time and inequality for date doesn't use the value function, which make the <= and >= operations useless and = operation behaves differently as < and >

Imagine the following two date and time values (note that both values are the same instant in time on the time line):

• date and time("2017-11-10T11:00@Europe/Paris")
• date and time("2017-11-10T10:00Z")

If the user uses FEEL expressions he is very surprised about the results:

date and time("2017-11-10T11:00@Europe/Paris") - date and time("2017-11-10T10:00Z")    -> result is PT0S, which means same instant on time line
date and time("2017-11-10T11:00@Europe/Paris") < date and time("2017-11-10T10:00Z")    -> result is false
date and time("2017-11-10T11:00@Europe/Paris") > date and time("2017-11-10T10:00Z")    -> result is false
date and time("2017-11-10T11:00@Europe/Paris") = date and time("2017-11-10T10:00Z")    -> result is false

If the user wants to check if both date and time values are the same instant on the time line he must use the following FEEL expression:

(date and time("2017-11-10T11:00@Europe/Paris") - date and time("2017-11-10T10:00Z")) = Duration("PT0S")

If the user uses a combination of < or > with = the underlying operations are not really understandable:

date and time("2017-11-10T11:00@Europe/Paris") >= date and time("2017-11-10T10:00Z")

This expressions says in the curently defined semantics in FEEL: "Is the left instant of time greater than the right instant in time or are the properties of the left value equal to the properties of the right value".

This is not "Friendly Enough" to the user and the source of very many misunderstandings.

Recommendation:

• Therefore the operators =, !=, <, >, <= and >= should ALL use the defined value functions.
• Additionally we recommend to introduce an additional property "value" for date, time, date and time, years and months duration, days and time duration (see table 53 on page 126). The property returns the value of the value function using type number.
• Introduce a new built-in function "same properties(value1, value2)" that compares all properties of value1 and value2 for equality. This built-in function reflects the currently specified behaviour of equality for date, date and time, time.

use timeline semantics for comparison of dates

see attached .docx file