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Timezone Discrepancies between GeoNames Timezone ID and PHP IANA/Olson Timezones

WARNING: This page is currently in need of updating. It has (or may have) outdated information. It will be updated, soon. You’ve been warned. For a useful table, see Time Zone Discrepancies between astro.com and IANA/Olson tz database.

This is a table of timezone discrepancies between two timezone databases:

1. Timezone id’s from GeoNames Timezone Database
2. PHP’s built-in Timezones from the IANA Time Zone Database (also known as Olson timezone database)

This table lists timezone id’s for specific latitude and longitude coordinates for historical times (a time in the past). This table lists cities and historical date-times which are wrong in either one of the 2 databases (GeoNames and/or IANA Timezone Databse).

*For both cases (Geonames Timezone ID & PHP/Iana/Olson Timezone ID), the offset is calculated by a PHP function. I don’t use the offset given by Geonames. The PHP function to calculate the offset takes the GeoNames Timezone ID in the 1st case, then the function takes the PHP Timezone ID in the second case.

The date format used below is MM/DD/YYYY.

The offset highlighted in green is the correct one for that row.

Post-1970 (Post Unix Epoch)
City Lat. Longit. Date Time GeoNames Timezone ID Offset * PHP Timezone ID Offset *
Hamlet, Indiana, USA
   (coordinates were incorrect at GeoNames which should
   be 41.54754, -86.58224)
41.381667 -86.584722 01/01/1992 12:00 p.m. America/Chicago -6 America/Indiana/Knox -5
Kazan, Russia 55.78874 49.12214 07/15/1973 7:52 a.m. Europe/Moscow 3 Europe/Samara 4
Chandigarh, India 30.73629 76.7884 3/6/1973 12:00 a.m. Asia/Kolkata 5.5 Asia/Kashgar 8
New Delhi, India 28.65195 77.23149 8/24/1989 5:20 p.m. Asia/Kolkata 5.5 Asia/Kathmandu 5.75

   

Pre-1970 (Pre Unix Epoch)
City Lat. Longit. Date Time GeoNames Timezone ID Offset * PHP Timezone ID Offset *
Houston, Texas, USA 29.76328 -95.36327 8/25/1949 7:52 a.m. America/Chicago -5 America/Matamoros -6

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