Support modern java.time types for getters (first draft)

[hczedik]

Add a getTemporal(.) method to Attributes which returns one of the modern java.time types (ZonedDateTime, LocalDateTime).

Motivation:

• The current timezone handling using the legacy Date type is a source of confusion and bugs, because it is unclear whether a timezone corrected date/time or a local date/zime is returned.
• The new types can store the full microsecond resolution that DICOM supports (no more rounding to millisecond, as it has to be done for the Date type)

@gunterze: This is a draft containing some TODOs. I just want to get your general feedback if you agree with the general design and whether I should continue working on this. Thanks!

[hczedik]

Note the different behavior here compared to getDefaultTimezone: It returns null in case nothing is defined and does not fall back to the system default.

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[gunterze]

Would prefer to do not consider the "corresponding" TM/DA attribute for DA/TM attributes.

Instead I propose to return

VR	&ZZXX	TimeZone	DST	Class
DT	yes	*	*	OffsetDateTime
DT	no	no	n/a	LocalDateTime
DT	no	yes	no	OffsetDateTime
DT	no	yes	yes	ZonedDateTime
DA	n/a	*	*	LocalDate
TM	n/a	no	n/a	LocalTime
TM	n/a	yes	no	OffsetTime
TM	n/a	yes	yes	LocalTime

for getTemporal(int tag), where TimeZone falls back to defaultTimeZone,

Alternatively to

VR	&ZZXX	TimeZone	DST	Class
TM	n/a	yes	yes	LocalTime

you may return

VR	&ZZXX	TimeZone	DST	Class
TM	n/a	yes	yes	OffsetTime

with setting as offset

• either the Offset of the TimeZone at current date and time
• or the Raw (without DST Saving) Offset of the TimeZone

And provide also getTemporal(long datmTag) (datmTag = (daTag << 32) | tmTag) returning

DA	TM	TimeZone	DST	Class
no	*	*	*	null
yes	no	*	*	LocalDate
yes	yes	no	n/a	LocalDateTime
yes	yes	*	*	OffsetDateTime
yes	yes	yes	no	OffsetDateTime
yes	yes	yes	yes	ZonedDateTime

Alternatively to

DA	TM	TimeZone	DST	Class
no	*	*	*	null

you may return

DA	TM	TimeZone	DST	Class
no	no	*	*	null
no	yes	no	n/a	LocalTime
no	yes	yes	no	OffsetTime
no	yes	yes	yes	LocalTime

and - as above - alternatively to

DA	TM	TimeZone	DST	Class
no	yes	yes	yes	LocalTime

you may return

DA	TM	TimeZone	DST	Class
no	yes	yes	yes	OffsetTime

with setting as offset

• either the Offset of the TimeZone at current date and time
• or the Raw (without DST Saving) Offset of the TimeZone

[hczedik]

Hi @gunterze ,

thanks a lot for the detailled feedback on this one. Sorry for the delay now on my side, I am busy with some other stuff at the moment. But I will definitely follow-up on this PR.

Thanks again!