Blog topic

Data quality (page 5)

Coverage by country, accuracy measurements, and how to read the precision and confidence in each answer.

1 September 2026 · 3 min read

Countries that have changed their time zone rules

A country's UTC offset is not permanent. Governments periodically redraw zone boundaries, adjust offsets, or add and drop daylight saving, and software has to keep up.

31 August 2026 · 2 min read

Daylight saving transitions and the requests that break around them

Twice a year, a range of local times either does not exist or exists twice. Software that assumes every clock time is unambiguous will fail exactly then.

31 August 2026 · 2 min read

Half-hour and 45-minute time zones, explained

Not every time zone sits on a clean hour boundary. Several countries use 30 or 45 minute offsets, and code that assumes whole hours will break on them.

30 August 2026 · 2 min read

Time zone data: how the rules actually get maintained

Time zone offsets are not fixed physical facts, they are legal decisions that governments change. Here is how that gets tracked and kept current.

30 August 2026 · 2 min read

Mobile carrier NAT and what it does to IP accuracy

Thousands of phones on the same carrier network can share one public IP address. That single fact explains most of the accuracy limits on mobile geolocation.

29 August 2026 · 2 min read

How VPNs and proxies affect IP-based location data

A VPN does not hide a user from IP geolocation, it just relocates them to the exit server. Here is what that means for the data you get back.

29 August 2026 · 2 min read

Why IP geolocation is a network estimate, not a street address

An IP address identifies a network connection, not a physical address. Understanding that distinction prevents most IP geolocation disappointment.

28 August 2026 · 2 min read

Reading the confidence and precision fields correctly

Precision tells you what kind of match you got. Confidence tells you how sure the geocoder is. Mixing up the two leads to bad filtering logic.

28 August 2026 · 3 min read

How we measure geocoding accuracy against known points

Accuracy claims mean nothing without a method. Here is how reference addresses with known coordinates are used to check what a geocoder actually returns.