Hi @Marcel den Ouden 

I did something similar a few years back for an ISC internal project.
I required 2 tables to achieve this
- mapping of the location to timezone code  (geographic coordinates are often misleading, STATIC)
- rules and offset from UTC (daylight Saving Y/N, the window when to apply,...) might be flexible
- $ZTZ is your friend and the Docs are really excellent also for special cases

A further complication is mobile use.
example:
- You go to Summit in Seattle. (UTC-7)
- you need to arrange a concall with a customer in Amsterdam (UTC+2) (CEST!)
- and meeting in Nov. (UTC+1)  back to normal time
- And you need to know the time zone used by your notebook (local or home or other?)

For the notebook, I used some JavaScript as the app was written in ZEN (10 yrs.back)
and it was mine and I could control it.
see more in my Article Global Time Management


 

From your description, it is obvious that you write ALL global streams just to default ^CacheStream.

To separate them you may set individual Globals for streaming (e.g depending on use-case)

Class %Library.GlobalBinaryStream has this parameter + property:

/// Default location: can be overridden at run-time
Parameter STOREGLOBALNAME = "^CacheStream"; /// Root is Global Location (name and top subscripts)

Property StoreRoot As %String(MAXLEN = 5000) [ InitialExpression = {..#STOREGLOBALNAME}, Private ]; Property rollback As %String [ MultiDimensional, Private ];

You can change this default using the method
Method %LocationSet(value As %String) As %Status
{
 Do ..Clear()
 Set ..StoreRoot=value,i%%Location=value
 Quit $$$OK
}
 

Default Samples.Person use the implicit ID.

You need to change or  write your own Method %IdSet or Define your own property as  ID

Suggestion:
add 

Property Val as Serials.Value;
in your main class
and
Class Serial.Value  Extends %SerialObject {
Property Single as %String;
Property Tsh as %String;
Property T4 as %String;
Property T5 as %String;
}  

in SQL you see it as columns 
Val_Single
Val_Tsh
Val_T4
Val_T5

$QUERY() needs a Global reference:

• ^je1("NotConfigured"   is OK
• node is just a local variable and not OK
• to use it you have to apply an indirection  >>> @node

I have edited my reply after the first send
and better use %node as indirection is context sensitive.