Merge pull request #1257 from heiglandreas/addReasonsNotToConvertToUtc

Add answer to a recurring question re UTC

Author: Jean85

proposed/clock-meta.md

@@ -137,3 +137,37 @@ This document stems from the work of many people in previous years, we recognize
 
  * 
 _**Note:** Order descending chronologically._
+
+## 9. FAQ
+
+### Why not simply use UTC?
+
+There are different reasons why this interface does not enforce a specific timezone.
+
+For one thing there is a purely technical reason. The interface provides an explicit contract. Part of this 
+contract is the value that is returned by the `now`-function. The only thing that currently can explicitly 
+be enforced on the language level is, that the returned value is of type `DateTimeImmutable`. There 
+currently is no way to enforce that this object has a certain timezone as its value. So from a language 
+level perspective there is no way to explicitly enforce a certain timezone in the returned object.
+
+On the other hand, there is also a logical reason. The explicit contract should be usable in all situations
+where one needs a way to retrieve the current time. And on the contract level we should not make an 
+assumption about what the caller might need. So would the contract define that only UTC is returned, then 
+use-cases that do require something else will have to explicitly work around that or find other ways of 
+handling the problem, the contract tries to solve as the contract does not fit the needs. This is different 
+from the issue of i.e., immutability which can also not be enforced on the language level but which is
+necessary to adhere to other calls on the contract. IN the case of the `clock`-interface there will be no 
+other calls.
+
+And most important of all, the explicit contract provided by this interface does not reduce a user’s
+possibilities to use an implicit contract within their application, that defines that the interface 
+will only return `DateTimeImmutable`s with a specific timezone set. And whether that is `UTC` or reduce
+`Antarctica/Troll` is completely up to the user. 
+
+The explicit contract that is defined by the interface does not limit a user in what they are doing. It 
+tries to solve the problem of getting the current time in a reliable way. Which view on the current time 
+that is, is not part of the explicit contract.
+
+So, all in all: This interface tries to be as open as possible while at the same time being as 
+strict as necessary.
+