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<p>It is known that pre-1970 time zone history is represented in TZ
database only for the cities which define the zone names.<br>
Other areas of countries are often not correctly represented in TZ
database before 1970.</p>
<p>The worst are the USA and Canada, because there, in many states,
the authority about daylight time adherence was in the hands of
counties or towns, up to the Uniform Timezone Act of 1967.<br>
</p>
<p>I am personally responsible for providing correct timezone
history for the astrological service company Astrodienst AG in
Switzerland, which runs among other things the website
<a class="moz-txt-link-abbreviated" href="http://www.astro.com">www.astro.com</a><br>
<br>
As source for timezone history we use, besides TZ database, the
International and American Atlas by Thomas Shanks, and our own
research.</p>
<p>The data we have are still far from perfect, because many local
details of time zone and daylight saving time use are unknown,
especially in the US and Canada.</p>
<p>We have about 25 million birth data records in our database.</p>
<p>I have analyzed to what extent TZ database represents the time
zone information correctly, for these data.</p>
<p>I think the results are of some interest for the TZ community.<br>
</p>
<p>The overall sums are:</p>
<p><tt>tz_count 24'674'767 data records, 100%</tt><tt><br>
</tt><tt>tz_irange 23'675'636 in time range and region which TZ
covers correctly, 96%</tt><tt><br>
</tt><tt>tz_good 736'769 </tt><tt>in time range and region
where TZ is unreliable, but correct</tt><tt>, 3%<br>
</tt><tt>tz_bad 262'362 </tt><tt>in time range and region
where TZ database gives false result. 1%</tt></p>
<p><tt>This means that only 1% of our astrological charts would be
false, if we used TZ database only, without any extra time zone
history sources.</tt></p>
<p><tt>More details by country or US/Canada state.<br>
state count in_range % good % bad %<br>
USA<br>
AK (US) 19889 99.6 0.0 0.3
Alaska<br>
AL (US) 64975 78.6 13.3 8.1
Alabama<br>
AR (US) 43159 77.2 12.7 10.0
Arkansas<br>
AZ (US) 96545 97.9 2.0 0.0
Arizona<br>
CA (US) 981941 100.0 0.0 0.0
California<br>
CO (US) 107204 99.5 0.5 0.0
Colorado<br>
CT (US) 89273 95.8 4.2 0.0
Connecticut<br>
DC (US) 58401 85.7 13.1 1.1
District of Columbia<br>
DE (US) 14376 91.3 8.5 0.3
Delaware<br>
FL (US) 241083 89.0 6.5 4.5
Florida<br>
GA (US) 114613 85.8 7.1 7.2
Georgia (US)<br>
HI (US) 44070 100.0 0.0 0.0
Hawaii<br>
IA (US) 50194 72.7 17.1 10.2
Iowa<br>
ID (US) 23877 92.2 6.4 1.4
Idaho<br>
IL (US) 267459 90.4 9.5 0.1
Illinois<br>
IN (US) 88263 76.8 21.6 1.6
Indiana<br>
KS (US) 45462 74.4 15.0 10.6
Kansas<br>
KY (US) 56494 74.6 12.5 12.9
Kentucky<br>
LA (US) 76017 80.3 11.9 7.8
Louisiana<br>
MA (US) 193439 87.1 12.9 0.1
Massachusetts<br>
MD (US) 91577 91.2 8.1 0.7
Maryland<br>
ME (US) 31873 96.8 2.8 0.5
Maine<br>
MI (US) 185568 86.0 13.3 0.7
Michigan<br>
MN (US) 95725 75.0 17.0 7.9
Minnesota<br>
MO (US) 91038 79.4 14.4 6.2
Missouri<br>
MS (US) 28859 70.0 20.4 9.6
Mississippi<br>
MT (US) 19767 73.7 24.7 1.5
Montana<br>
NC (US) 106991 82.9 10.2 6.9
North Carolina<br>
ND (US) 12427 71.5 17.5 10.9
North Dakota<br>
NE (US) 28670 69.1 18.2 12.7
Nebraska<br>
NH (US) 23707 91.2 8.2 0.6
New Hampshire<br>
NJ (US) 190614 99.6 0.3 0.1
New Jersey<br>
NM (US) 42651 80.6 18.4 0.9
New Mexico<br>
NV (US) 36053 99.4 0.4 0.3
Nevada<br>
NY (US) 628944 96.8 3.0 0.1
New York<br>
OH (US) 191745 73.9 18.3 7.8
Ohio<br>
OK (US) 55229 73.7 16.5 9.8
Oklahoma<br>
OR (US) 98166 87.1 9.8 3.1
Oregon<br>
PA (US) 228064 89.8 9.7 0.6
Pennsylvania<br>
PR (US) 37149 100.0 0.0 0.0
Puerto Rico<br>
RI (US) 26089 97.1 2.8 0.1
Rhode Island<br>
SC (US) 40233 82.9 10.0 7.1
South Carolina<br>
SD (US) 12863 72.7 18.6 8.7
South Dakota<br>
TN (US) 75125 82.9 9.3 7.8
Tennessee<br>
TX (US) 327328 83.3 9.8 6.9
Texas<br>
UT (US) 48909 82.7 16.2 1.1
Utah<br>
VA (US) 109591 85.5 10.1 4.4
Virginia<br>
VT (US) 17598 86.4 12.7 0.9
Vermont<br>
WA (US) 159835 84.8 11.9 3.3
Washington<br>
WI (US) 85917 75.5 18.5 5.9
Wisconsin<br>
WV (US) 22800 72.7 20.3 7.0
West Virginia<br>
WY (US) 8962 75.1 23.9 0.9
Wyoming</tt></p>
<p><tt><br>
Canada<br>
AB (CAN) 64249 97.9 2.0 0.1
Alberta<br>
BC (CAN) 99214 98.0 2.0 0.0
British Columbia (CAN)<br>
MB (CAN) 21563 69.8 27.5 2.6
Manitoba (CAN)<br>
NB (CAN) 10438 89.0 8.3 2.7
New Brunswick (CAN)<br>
NF (CAN) 7329 98.4 1.2 0.4
Newfoundland (CAN)<br>
NS (CAN) 18829 75.4 16.3 8.2
Nova Scotia (CAN)<br>
NT (CAN) 1137 80.7 0.0 19.3
Northwest Territories (CAN)<br>
ON (CAN) 239755 86.3 12.4 1.3
Ontario (CAN)<br>
PE (CAN) 2036 80.0 16.1 3.9
Prince Edward Island (CAN)<br>
QU (CAN) 126300 88.4 9.8 1.8
Quebec (CAN)<br>
SK (CAN) 24390 78.2 12.4 9.5
Saskatchewan (CAN)<br>
YK (CAN) 932 100.0 0.0 0.0
Yukon Territories (CAN)<br>
<br>
Other countries with significant issues in TZ database, only
those with > 1% bad results<br>
BY 13966 97.1 1.2 1.7
Belarus<br>
CAR 268 33.2 0.4 66.4
Central African Repub<br>
CHINA 214617 96.0 2.4 1.6
China<br>
CONGO 1026 49.9 0.0 50.1
Congo (Brazaville)<br>
GABON 704 47.7 0.0 52.3
Gabon<br>
GUAM 3613 45.6 0.0 54.4
Guam<br>
INDSA 51950 97.2 0.8 2.0
Indonesia<br>
NIGER 294 76.9 3.7 19.4
Niger<br>
NIRE (UK) 16228 97.1 0.7 2.1
Northern Ireland<br>
RU 177880 89.4 8.5 2.1
Russian Federation<br>
SUDAN 2495 0.0 0.0 100.0
Sudan (?? my be my fault)<br>
TAAF 2 0.0 0.0 100.0
French Kerguelen Islands<br>
TANZ 4162 68.3 30.2 1.5
Tanzania<br>
TOK 17 41.2 0.0 58.8
Tokelau<br>
UA 71260 95.9 2.4 1.7
Ukraine<br>
VIET 299630 97.6 0.8 1.6
Vietnam<br>
</tt></p>
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