Use bits in .RYEAR/.RLPDTM result to return a local time zone,
TZONE (definable in SYSTEM;CONFIG).
TZONE should be the integer timezone offset (hours West of UTC)
Bit 4.4 => timezone known (otherwise, assume EST/EDT = 5)
Bit 4.3 => sign bit of timezone offset
Bits 3.5-3.1 => absolute value of timezone offset
If DSTEU is defined and != 0, calculate daylight savings time
according to European Union rules:
- starts at 2:00 (standard time) on the last Sunday in March,
- ends at 2:00 (standard time) on the last Sunday in October.
