This is a fast and lightweight python project for looking up the corresponding timezone for a given lat/lng on earth entirely offline.
NOTE: tz_world is not being maintained any more and the new data (s. below) is unfortunately much bigger (40+MB). I am sorry for this, but at least it is up to date. In case size and speed matter more you than actuality, consider checking out older versions of timezonefinder(L). The timezone polygons also do NOT follow the shorelines any more (as they did with tz_world). This makes the results of closest_timezone_at() somewhat meaningless (as with timezonefinderL).
The underlying timezone data is now based on work done by Evan Siroky. Current version: 2017a (March 2017, since 2.1.0) Previously: tz_world 2016d (May 2016, until 2.0.2)
Also see: GitHub, PyPI, conda-forge feedstock, timezone_finder (ruby port)
This project is derived from and has been successfully tested against pytzwhere (github), but aims at providing improved performance and usability.
pytzwhere is parsing a 76MB .csv file (floats stored as strings!) completely into memory and computing shortcuts from this data on every startup. This is time, memory and CPU consuming. Additionally calculating with floats is slow, keeping those 4M+ floats in the RAM all the time is unnecessary and the precision of floats is not even needed in this case (s. detailed comparison and speed tests below).
Check out the even faster and lighter (but outdated) version timezonefinderL and its demo and API at: timezonefinderL GUI
(python) numpy
Optional:
Numba (https://github.com/numba/numba) and its Requirement llvmlite
This is only for precompiling the time critical algorithms. When you only look up a few points once in a while, the compilation time is probably outweighing the benefits. When using certain_timezone_at() and especially closest_timezone_at() however, I highly recommend using numba!
Installation with conda: see instructions at conda-forge feedstock
Installation with pip: in the command line:
pip install timezonefinderin Python:
from timezonefinder import TimezoneFinder
tf = TimezoneFinder()for testing if numba is being used: (if the import of the optimized algorithms worked)
TimezoneFinder.using_numba() # this is a static method returning True or Falsetimezone_at():
This is the default function to check which timezone a point lies within (similar to tzwheres tzNameAt()). If no timezone has been found, None is being returned.
PLEASE NOTE: This approach is optimized for speed and the common case to only query points within a timezone. The last possible timezone in proximity is always returned (without checking if the point is really included). So results might be misleading for points outside of any timezone.
longitude = 13.358
latitude = 52.5061
tf.timezone_at(lng=longitude, lat=latitude) # returns 'Europe/Berlin'certain_timezone_at():
This function is for making sure a point is really inside a timezone. It is slower, because all polygons (with shortcuts in that area) are checked until one polygon is matched.
tf.certain_timezone_at(lng=longitude, lat=latitude) # returns 'Europe/Berlin'closest_timezone_at():
Only use this when the point is not inside a polygon, because the approach otherwise makes no sense. This returns the closest timezone of all polygons within +-1 degree lng and +-1 degree lat (or None).
longitude = 12.773955
latitude = 55.578595
tf.closest_timezone_at(lng=longitude, lat=latitude) # returns 'Europe/Copenhagen'Other options: To increase search radius even more, use the delta_degree-option:
tf.closest_timezone_at(lng=longitude, lat=latitude, delta_degree=3)This checks all the polygons within +-3 degree lng and +-3 degree lat. I recommend only slowly increasing the search radius, since computation time increases quite quickly (with the amount of polygons which need to be evaluated). When you want to use this feature a lot, consider using Numba to save computing time.
Also keep in mind that x degrees lat are not the same distance apart than x degree lng (earth is a sphere)! As a consequence getting a result does NOT mean that there is no closer timezone! It might just not be within the area being queried.
With exact_computation=True the distance to every polygon edge is computed (way more complicated), instead of just evaluating the distances to all the vertices. This only makes a real difference when polygons are very close.
With return_distances=True the output looks like this:
( 'tz_name_of_the_closest_polygon',[ distances to every polygon in km], [tz_names of every polygon])
Note that some polygons might not be tested (for example when a zone is found to be the closest already). To prevent this use force_evaluation=True.
longitude = 42.1052479
latitude = -16.622686
tf.closest_timezone_at(lng=longitude, lat=latitude, delta_degree=2,
exact_computation=True, return_distances=True, force_evaluation=True)
'''
returns ('uninhabited',
[80.66907784731714, 217.10924866254518, 293.5467252349301, 304.5274937839159, 238.18462606485667, 267.918674688949, 207.43831938964408, 209.6790144988553, 228.42135641542546],
['uninhabited', 'Indian/Antananarivo', 'Indian/Antananarivo', 'Indian/Antananarivo', 'Africa/Maputo', 'Africa/Maputo', 'Africa/Maputo', 'Africa/Maputo', 'Africa/Maputo'])
'''get_geometry:
for querying timezones for their geometric shape use get_geometry(). output format: [ [polygon1, hole1,...), [polygon2, ...], ...] and each polygon and hole is itself formated like: ([longitudes], [latitudes]) or [(lng1,lat1), (lng2,lat2),...] if coords_as_pairs=True.
tf.get_geometry(tz_name='Africa/Addis_Ababa', coords_as_pairs=True)
tf.get_geometry(tz_id=400, use_id=True)To maximize the chances of getting a result in a Django view it might look like:
def find_timezone(request, lat, lng):
lat = float(lat)
lng = float(lng)
try:
timezone_name = tf.timezone_at(lng=lng, lat=lat)
if timezone_name is None:
timezone_name = tf.closest_timezone_at(lng=lng, lat=lat)
# maybe even increase the search radius when it is still None
except ValueError:
# the coordinates were out of bounds
# {handle error}
# ... do something with timezone_name ...To get an aware datetime object from the timezone name:
# first pip install pytz
from pytz import timezone, utc
from pytz.exceptions import UnknownTimeZoneError
# tzinfo has to be None (means naive)
naive_datetime = YOUR_NAIVE_DATETIME
try:
tz = timezone(timezone_name)
aware_datetime = naive_datetime.replace(tzinfo=tz)
aware_datetime_in_utc = aware_datetime.astimezone(utc)
naive_datetime_as_utc_converted_to_tz = tz.localize(naive_datetime)
except UnknownTimeZoneError:
# ... handle the error ...also see the pytz Doc.
parsing the data:
Download the latest .json from GitHub. Place it inside the timezonefinder folder and run the file_converter.py first only until the timezone_names.py have been updated. Then abort and rerun file_converter.py, this time until the compilation of the binary files is completed. (compilation need to import the new timezone_names.py file)
Calling timezonefinder from the command line:
With -v you get verbose output, without it only the timezone name is printed. Internally this is calling the function timezone_at(). Please note that this is slow.
python timezonefinder.py lng lat [-v]I ran tests for approx. 5M points and the only differences (in comparison to tzwhere) are due to the outdated data being used by tzwhere.
Most certainly there is stuff I missed, things I could have optimized even further etc. I would be really glad to get some feedback on my code.
If you notice that the tz data is outdated, encounter any bugs, have suggestions, criticism, etc. feel free to open an Issue, add a Pull Requests on Git or ...
contact me: [python] {at} [michelfe] {dot} [it]
Thanks to:
Adam for adding organisational features to the project and for helping me with publishing and testing routines.
cstich for the little conversion script (.shp to .json).
snowman2 for creating the conda-forge recipe.
synapticarbors for fixing Numba import with py27.
timezonefinder is distributed under the terms of the MIT license (see LICENSE.txt).
In comparison most notably initialisation time and memory usage are significantly reduced, while the algorithms yield the same results and are as fast or even faster (depending on the dependencies used, s. test results below). pytzwhere is using up to 450MB!!! of RAM while in use (with shapely and numpy active) and this package uses at most 40MB (= encountered memory consumption of the python process). In some cases pytzwhere even does not find anything and timezonefinder does, for example when only one timezone is close to the point.
Similarities:
- results
- data being used
Differences:
- highly decreased memory usage
- highly reduced start up time
- usage of 32bit int (instead of 64+bit float) reduces computing time and memory consumption
- the precision of 32bit int is still high enough (according to my calculations worst resolution is 1cm at the equator -> far more precise than the discrete polygons)
- the data is stored in memory friendly binary files (approx. 41MB in total, original data 120MB .json)
- data is only being read on demand (not completely read into memory if not needed)
- precomputed shortcuts are included to quickly look up which polygons have to be checked
- available proximity algorithm
closest_timezone_at() - function
get_geometry()enables querying timezones for their geometric shape (= multipolygon with holes) - further speedup possible by the use of
numba(code precompilation)
:
test correctness:
results timezone_at()
LOCATION | EXPECTED | COMPUTED | ==
====================================================================
Arlington, TN | America/Chicago | America/Chicago | OK
Memphis, TN | America/Chicago | America/Chicago | OK
Anchorage, AK | America/Anchorage | America/Anchorage | OK
Eugene, OR | America/Los_Angeles | America/Los_Angeles | OK
Albany, NY | America/New_York | America/New_York | OK
Moscow | Europe/Moscow | Europe/Moscow | OK
Los Angeles | America/Los_Angeles | America/Los_Angeles | OK
Moscow | Europe/Moscow | Europe/Moscow | OK
Aspen, Colorado | America/Denver | America/Denver | OK
Kiev | Europe/Kiev | Europe/Kiev | OK
Jogupalya | Asia/Kolkata | Asia/Kolkata | OK
Washington DC | America/New_York | America/New_York | OK
St Petersburg | Europe/Moscow | Europe/Moscow | OK
Blagoveshchensk | Asia/Yakutsk | Asia/Yakutsk | OK
Boston | America/New_York | America/New_York | OK
Chicago | America/Chicago | America/Chicago | OK
Orlando | America/New_York | America/New_York | OK
Seattle | America/Los_Angeles | America/Los_Angeles | OK
London | Europe/London | Europe/London | OK
Church Crookham | Europe/London | Europe/London | OK
Fleet | Europe/London | Europe/London | OK
Paris | Europe/Paris | Europe/Paris | OK
Macau | Asia/Macau | Asia/Macau | OK
Russia | Asia/Yekaterinburg | Asia/Yekaterinburg | OK
Salo | Europe/Helsinki | Europe/Helsinki | OK
Staffordshire | Europe/London | Europe/London | OK
Muara | Asia/Brunei | Asia/Brunei | OK
Puerto Montt seaport | America/Santiago | America/Santiago | OK
Akrotiri seaport | Asia/Nicosia | Asia/Nicosia | OK
Inchon seaport | Asia/Seoul | Asia/Seoul | OK
Nakhodka seaport | Asia/Vladivostok | Asia/Vladivostok | OK
Truro | Europe/London | Europe/London | OK
Aserbaid. Enklave | Asia/Baku | Asia/Baku | OK
Tajikistani Enklave | Asia/Dushanbe | Asia/Dushanbe | OK
Busingen Ger | Europe/Busingen | Europe/Busingen | OK
Genf | Europe/Zurich | Europe/Zurich | OK
Lesotho | Africa/Maseru | Africa/Maseru | OK
usbekish enclave | Asia/Tashkent | Asia/Tashkent | OK
usbekish enclave | Asia/Tashkent | Asia/Tashkent | OK
Arizona Desert 1 | America/Denver | America/Denver | OK
Arizona Desert 2 | America/Phoenix | America/Phoenix | OK
Arizona Desert 3 | America/Phoenix | America/Phoenix | OK
Far off Cornwall | None | None | OK
certain_timezone_at():
LOCATION | EXPECTED | COMPUTED | Status
====================================================================
Arlington, TN | America/Chicago | America/Chicago | OK
Memphis, TN | America/Chicago | America/Chicago | OK
Anchorage, AK | America/Anchorage | America/Anchorage | OK
Eugene, OR | America/Los_Angeles | America/Los_Angeles | OK
Albany, NY | America/New_York | America/New_York | OK
Moscow | Europe/Moscow | Europe/Moscow | OK
Los Angeles | America/Los_Angeles | America/Los_Angeles | OK
Moscow | Europe/Moscow | Europe/Moscow | OK
Aspen, Colorado | America/Denver | America/Denver | OK
Kiev | Europe/Kiev | Europe/Kiev | OK
Jogupalya | Asia/Kolkata | Asia/Kolkata | OK
Washington DC | America/New_York | America/New_York | OK
St Petersburg | Europe/Moscow | Europe/Moscow | OK
Blagoveshchensk | Asia/Yakutsk | Asia/Yakutsk | OK
Boston | America/New_York | America/New_York | OK
Chicago | America/Chicago | America/Chicago | OK
Orlando | America/New_York | America/New_York | OK
Seattle | America/Los_Angeles | America/Los_Angeles | OK
London | Europe/London | Europe/London | OK
Church Crookham | Europe/London | Europe/London | OK
Fleet | Europe/London | Europe/London | OK
Paris | Europe/Paris | Europe/Paris | OK
Macau | Asia/Macau | Asia/Macau | OK
Russia | Asia/Yekaterinburg | Asia/Yekaterinburg | OK
Salo | Europe/Helsinki | Europe/Helsinki | OK
Staffordshire | Europe/London | Europe/London | OK
Muara | Asia/Brunei | Asia/Brunei | OK
Puerto Montt seaport | America/Santiago | America/Santiago | OK
Akrotiri seaport | Asia/Nicosia | Asia/Nicosia | OK
Inchon seaport | Asia/Seoul | Asia/Seoul | OK
Nakhodka seaport | Asia/Vladivostok | Asia/Vladivostok | OK
Truro | Europe/London | Europe/London | OK
Aserbaid. Enklave | Asia/Baku | Asia/Baku | OK
Tajikistani Enklave | Asia/Dushanbe | Asia/Dushanbe | OK
Busingen Ger | Europe/Busingen | Europe/Busingen | OK
Genf | Europe/Zurich | Europe/Zurich | OK
Lesotho | Africa/Maseru | Africa/Maseru | OK
usbekish enclave | Asia/Tashkent | Asia/Tashkent | OK
usbekish enclave | Asia/Tashkent | Asia/Tashkent | OK
Arizona Desert 1 | America/Denver | America/Denver | OK
Arizona Desert 2 | America/Phoenix | America/Phoenix | OK
Arizona Desert 3 | America/Phoenix | America/Phoenix | OK
Far off Cornwall | None | None | OK
closest_timezone_at():
LOCATION | EXPECTED | COMPUTED | Status
====================================================================
Arlington, TN | America/Chicago | America/Chicago | OK
Memphis, TN | America/Chicago | America/Chicago | OK
Anchorage, AK | America/Anchorage | America/Anchorage | OK
Shore Lake Michigan | America/New_York | America/New_York | OK
English Channel1 | Europe/London | Europe/London | OK
English Channel2 | Europe/Paris | Europe/Paris | OK
Oresund Bridge1 | Europe/Stockholm | Europe/Stockholm | OK
Oresund Bridge2 | Europe/Copenhagen | Europe/Copenhagen | OK
Speed Tests:
_________________________
shapely: OFF (tzwhere)
Numba: OFF (timezonefinder)
Startup times:
tzwhere: 0:00:07.875212
timezonefinder: 0:00:00.000688
11445.53 times faster
_________________________
shapely: ON (tzwhere)
Numba: ON (timezonefinder)
Startup times:
tzwhere: 0:00:29.365294
timezonefinder: 0:00:00.000888
33068.02 times faster
NOTE: all the other test are not expressive atm, because tz_where is using very outdated data
\* System: MacBookPro 2,4GHz i5 (2014) 4GB RAM pytzwhere with numpy active
\*\*mismatch: pytzwhere finds something and then timezonefinder finds
something else
\*\*\*realistic queries: just points within a timezone (= pytzwhere
yields result)
\*\*\*\*random queries: random points on earth
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