Add support of UTC plus an additional local time date patterns

We would like to have the following three UTC plus an addition local time date pattern supported by the DATETIME and REPATTERN built-in functions:

1) 'YYYY-MM-DDTHH:MI:SS.999S99:99'
2) 'YYYY-MM-DDTHH:MI:SS.999Z'
3) 'YYYY-MM-DDTHH:MI:SS.999 UTC'
4) 'YYYY-MM-DDTHH:MI:SS.999' (local time)

1) would be understood to hold a UTC-plus-offset or extended-UTC value.
2) and 3) would be understood to hold a UTC value.
4) is the equivalent pattern in local time.

REPATTERN will have to support the converting between UTC and local time as follows:

UTC date pattern as source:
- When converting from an extended-UTC date to something other than a UTC date, the offset value will be added to the hours and minutes part (as I think you wanted in your note below)
- When converting from an extended-UTC date to a UTC date, the offset value will be ignored if the target is not an extended-UTC date (otherwise it will be copied)
- When converting any other UTC date to an extended-UTC date, the offset value will be set to +00:00
- When converting any other UTC date to any other date, there will be no attempt to adjust for the local time: the date/time parts will simply be adjusted as needed

UTC date pattern as target:
- When converting to an extended UTC format, the offset value will be set to +00:00 unless the source is also an extended UTC date
- When converting to any other UTF format, there will be no attempt to adjust for the local time: the date/time parts will simply be adjusted as needed
- So, for both of these scenarios, the user is responsible for insuring that the source holds a UTC value - as would be true if the source were obtained from the UTCDateTime function