This is an automated email from the ASF dual-hosted git repository.
paulk pushed a commit to branch asf-site
in repository https://gitbox.apache.org/repos/asf/groovy-website.git
The following commit(s) were added to refs/heads/asf-site by this push:
new 7a1dff5 additional blog
7a1dff5 is described below
commit 7a1dff5d9abda5336ac46fed6c13c3840bc7f52a
Author: Paul King <[email protected]>
AuthorDate: Mon Feb 20 22:09:56 2023 +1000
additional blog
---
site/src/site/blog/australian-timezones.adoc | 253 ++++++++++++++++++++++++
site/src/site/blog/img/perth_eucla_adelaide.png | Bin 0 -> 74480 bytes
2 files changed, 253 insertions(+)
diff --git a/site/src/site/blog/australian-timezones.adoc
b/site/src/site/blog/australian-timezones.adoc
new file mode 100644
index 0000000..9efd17e
--- /dev/null
+++ b/site/src/site/blog/australian-timezones.adoc
@@ -0,0 +1,253 @@
+= Australian Time Zones
+Paul King
+:revdate: 2023-02-202T20:00:00+00:00
+:keywords: groovy, datetime, timezone, date
+:description: Inspired by a recent update related to Antarctic timezones, this
post looks at some interesting Australian time zone facts.
+
+https://kenkousen.substack.com/[Ken Kousen] posted another
+https://t.co/VM4f4lpM7a[Tales from the jar side] episode
+covering among other things, time zones in Antarctica.
+
+image:https://external-preview.redd.it/16_JjhwH0lSETAc7LMNvulifXMrs-43lWIs_nr2OPIs.jpg?width=960&crop=smart&auto=webp&v=enabled&s=7fe189e9ed24d481d3445fad245bd6ae18ee5740[Research
stations and timezones in Antarctica]
+
+Let's replicate his example in Groovy before looking at time zones
+more broadly in Australia. Why Australia? Well, that's where I'm from but also
+there's a reference in Ken's article to one of the facts we'll look at. First,
here
+is the equivalent of Ken's exploration at the South Pole:
+
+[subs="quotes"]
+----
+[lime]*Groovy Shell* (4.0.9, JVM: 17.0.2)
+Type ':help' or ':h' for help.
+-------------------------------------------------------------------------------
+groovy:000> import java.time.*
+===> java.time.*
+groovy:000> southPole = ZoneId.of('Antarctica/South_Pole')
+===> Antarctica/South_Pole
+groovy:000> dst = southPole.rules.isDaylightSavings(Instant.now())
+===> true
+groovy:000> "The South Pole ${dst ? 'IS' : 'IS NOT'} currently on DST"
+===> The South Pole IS currently on DST
+groovy:000>
+----
+
+Without wanting to give away Ken's punch line, the South Pole,
+in particular, the Amundsen-Scott station, is currently on daylight saving
time.
+Read https://t.co/VM4f4lpM7a[his article]
+or attend one of Ken's talks if you wonder why that might be strange!
+
+Speaking of strange, Ken also mentioned another strange fact related
+to Australian timezones. Australia has a zone, Eucla, with a 45-minute offset.
+And that's not the only interesting fact!
+
+Let's look at all Australian timezones, including Eucla, and the three
+Antarctic research stations, Casey, Davis, and Mawson
+(seen on the right of the above map).
+
+Before we dive into coding, let's look at the timezones we're interested in:
+
+[cols="1,3,2,5"]
+|===
+| Abbreviation | Time zone name | Offset | Where used
+
+| https://www.timeanddate.com/time/zones/acdt[ACDT]
+| Australian Central Daylight Time
+| UTC +10:30
+| _Summer:_ South Australia, Broken Hill/Yancowinna County in New South Wales
+
+| https://www.timeanddate.com/time/zones/acst[ACST]
+| Australian Central Standard Time
+| UTC +9:30
+| _Winter:_ South Australia, Broken Hill/Yancowinna County in New South Wales +
+_All year:_ Northern Territory
+
+| https://www.timeanddate.com/time/zones/act-australia[ACT]
+| Australian Central Time
+|
+| Often used as an abbreviation for places which switch between ACDT/ACST
+
+| https://www.timeanddate.com/time/zone/australia/eucla[ACWST]
+| Australian Central Western Standard Time
+| UTC +8:45
+| Eucla
+
+| https://www.timeanddate.com/time/zones/aedt[AEDT]
+| Australian Eastern Daylight Time
+| UTC +11
+| _Summer:_ Australian Capital Territory, New South Wales except Broken
Hill/Yancowinna County in New South Wales, Tasmania, Victoria +
+_All year:_ Macquarie Island
+
+| https://www.timeanddate.com/time/zones/aest[AEST]
+| Australian Eastern Standard Time
+| UTC +10
+| _Winter:_ Australian Capital Territory, New South Wales except Broken
Hill/Yancowinna County in New South Wales, Tasmania, Victoria +
+_All year:_ Queensland, Coral Sea Islands
+
+| https://www.timeanddate.com/time/zones/aet[AET]
+| Australian Eastern Time
+|
+| Often used as an abbreviation for places in either AEDT or AEST (or
switching between them)
+
+| https://www.timeanddate.com/time/zones/awdt[AWDT]
+| Australian Western Daylight Time
+| UTC +9
+| _Not currently in use_
+
+| https://www.timeanddate.com/time/zones/awst[AWST]
+| Australian Western Standard Time
+| UTC +8
+| Western Australia, Ashmore and Cartier Islands
+
+| https://www.timeanddate.com/time/zones/cct[CCT]
+| Cocos Islands Time
+| UTC +6:30
+| Cocos (Keeling) Islands
+
+| https://www.timeanddate.com/time/zones/cxt[CXT]
+| Christmas Island Time
+| UTC +7
+| Christmas Island
+
+| https://www.timeanddate.com/time/zones/lhdt[LHDT]
+| Lord Howe Daylight Time
+| UTC +11
+| _Summer:_ Lord Howe Island
+
+| https://www.timeanddate.com/time/zones/lhst[LHST]
+| Lord Howe Standard Time
+| UTC +10:30
+| _Winter:_ Lord Howe Island
+
+| https://www.timeanddate.com/time/zones/nfdt[NFDT]
+| Norfolk Daylight Time
+| UTC +12
+| _Summer:_ Norfolk Island
+
+| https://www.timeanddate.com/time/zones/nft[NFT]
+| Norfolk Time
+| UTC +11
+| _Winter:_ Norfolk Island
+
+| https://www.timeanddate.com/time/zones/tft[TFT]
+| French Southern and Antarctic Time
+| UTC +5
+| Heard and McDonald Islands
+
+| https://www.timeanddate.com/time/zones/cast[CAST]
+| Casey Time
+| _Winter:_ UTC +8 +
+_Summer:_ UTC +11
+| Casey Antarctic Station
+
+| https://www.timeanddate.com/time/zones/davt[DAVT]
+| Davis Time
+| UTC +7
+| Davis Antarctic Station
+
+| https://www.timeanddate.com/time/zones/mawt[MAWT]
+| Mawson Time
+| UTC +5
+| Mawson Antarctic Station
+|===
+
+Most countries have whole number zone offsets, but you
+should notice that Australia has many 30-minute offsets too.
+Ken mentioned that 45-minute offsets are even rarer (3 in the world).
+Let's look at Australia's contribution to that exclusive club:
+
+[source,groovy]
+----
+var eucla = ZoneId.of('Australia/Eucla')
+println eucla.rules.getStandardOffset(now)
+----
+
+This has the following result:
+
+----
++08:45
+----
+
+Why such a strange offset? Well, Eucla sits on the Nullarbor plain,
+about halfway between Perth and Adelaide, and close to the state border.
+It was once home to a telegram station and
+http://www.drivemelbournetoperth.com.au/time-zones-across-nullarbor.html#:~:text=To%20sort%20this%20issue%20out,time%20zone%20of%2045%20minutes[the
story goes] that to minimise confusion between the West Australian and
+South Australian workers who sat side-by-side sorting telegrams,
+they set the time zone to exactly halfway between their respective state
+timezones. Western Australia and South Australia are (excluding daylight
saving)
+an hour and 30 minutes apart, so halfway between results in the 45-minute
offset!
+
+image:img/perth_eucla_adelaide.png[Perth to Adelaide via Eucla]
+
+Incidentally, if you want to see
+the longest straight section of railway in the world (478 km, 297 mi),
+or the longest straight section of tarred road in Australia (146 km, 91 mi),
+then the Nullarbor plain is the place to be, but otherwise it's not high
+on most folks tourist attractions must-see list.
+
+image:https://upload.wikimedia.org/wikipedia/commons/thumb/9/91/Highway_sign%2C_Nullarbor%2C_2017_%2802%29.jpg/1920px-Highway_sign%2C_Nullarbor%2C_2017_%2802%29.jpg[Nullarbor
plain,600]
+
+Another obscure timezone fact related to the Nullarbor.
+When the Indian Pacific train travels between
+Kalgoorlie, Western Australia and Port Augusta, South Australia,
+it has its own time known as
+https://en.wikipedia.org/wiki/Time_in_Australia#:~:text=The%20Indian%20Pacific%20train%20has,the%20eastern%20and%20southern%20states["Train
Time"] (UTC+09:00).
+We won't follow this unofficial timezone in our later exploration,
+but it would add another to our list if we wanted to include it too!
+
+Another strange timezone fact applies to the pristine Lord Howe Island.
+Lord Howe Island is a little over 600 km out from the north coast of New South
Wales.
+That's about 1/4 of the way to New Zealand! Being that far East of the
mainland,
+it rightly has a timezone 30 minutes earlier than the mainland.
+
+image:https://www.thesenior.com.au/images/transform/v1/crop/frm/ezJUJGp6GbYvhKygBYtWTb/90dd6397-e247-4c3f-aacf-bd15b7cf8586.jpg/r0_31_600_371_w1200_h678_fmax.jpg[Lord
Howe Island]
+
+Apparently, some years back,
+https://www.atlasobscura.com/places/lord-howe-islands-time#:~:text=The%20reason%20for%20this%20unique,UTC%20%2B10%3A00%20clock[the
governor wanted to have a timezone coinciding
+with the mainland], for at least part of the year, so they held a referendum
+and voted in a 30-minute daylight saving time during Summer.
+
+Let's check this phenomenon:
+
+[source,groovy]
+----
+var lordHowe = ZoneId.of('Australia/Lord_Howe')
+assert lordHowe.rules.getDaylightSavings(now).toMinutes() == 30
+----
+
+Another Island timezone anomaly applies to Heron Island, 72 km (45 mi) off the
+coast of Gladstone in Queensland. It has two time zones: the island resort
follows
+daylight saving time all year round, whereas "the Marine Research Centre and
the Parks and Wildlife office on the island remain on Eastern Standard Time.
+
+Finally, let's collect all the different offsets applicable to Australia:
+
+[source,groovy]
+----
+var ids = ['Australia/Tasmania', 'Antarctica/Davis',
+ 'Australia/ACT', 'Australia/Eucla', 'Australia/North',
'Australia/Yancowinna',
+ 'Australia/Victoria', 'Australia/Adelaide', 'Antarctica/Mawson',
'Antarctica/Casey',
+ 'Australia/Queensland', 'Australia/Lord_Howe', 'Australia/NSW',
'Australia/South',
+ 'Australia/West', 'Indian/Christmas', 'Indian/Cocos', 'Pacific/Norfolk']
+Set offsets = []
+for (id in ids) {
+ var rules = ZoneId.of(id).rules
+ offsets << rules.getStandardOffset(now) // non daylight saving offset
+ offsets << rules.getOffset(now) // daylight saving offset when run
in Summer
+}
+----
+
+Let's check that there are 10 different offsets we need to deal with in
+Australian territories, with 4 being the less usual _not-on-the-hour_ offsets.
+Then, we'll print out the offsets.
+
+[source,groovy]
+----
+assert offsets.size() == 10
+assert offsets*.toString().count{ !it.endsWith(':00')} == 4
+println offsets
+----
+
+The two assertions pass and the final println has the following output:
+
+----
+[+10:00, +11:00, +07:00, +08:45, +09:30, +10:30, +05:00, +08:00, +06:30,
+12:00]
+----
diff --git a/site/src/site/blog/img/perth_eucla_adelaide.png
b/site/src/site/blog/img/perth_eucla_adelaide.png
new file mode 100644
index 0000000..8b29030
Binary files /dev/null and b/site/src/site/blog/img/perth_eucla_adelaide.png
differ
