What llttz is?

llttz (stands for latitude longitude to time zone) is a light-weight project written in Java which allows you to obtain the time zone in a place with specified latitude and longitude. Original idea (along with the dataset) was taken from the APTimezones project. To obtain the TimeZone you need to create an object of Converter class, and invoke its getInstance(double lat, double lon) method, like so:

IConverter iconv = Converter.getInstance(TimeZoneListStore.class);
TimeZone tz = iconv.getTimeZone(53.5233333, 49.4125);

Here TimeZoneListStore is a class which holds a list of timezones. The time complexity of nearest neighbor search is O(n) in that case. There is also another class, named TimeZoneTreeStore, which you can use to perform nearest neighbor searches. It holds a simple implementation of k-d tree which can perform nearest neighbor lookup with the time complexity of 0(ln(n)) in the best case (it's a little bit unstable and returns wrong timezones when we perform searches in the areas which are located near the South or North Pole so you can stick to TimeZoneListStore for now).

I see that you're using a list of timezones here instead of the list of timezones' polygones. The calculated time zone won't be precise, right?

Yes, in some cases you can get the error in +\- 2 hours.

Is it useful then?

It depends. In my case I needed library which could allow me to calculate the time zone by provided latitude/longitude without making requests to remote web-services, such as GeoNames. I also needed this library to be a light-weight (I had to use it on Android devices) and preciseness in calculations wasn't the mandatory requirement.