About Bestimez
Data sources, methodology, and accuracy standards behind our timezone tools.
What is Bestimez?
Bestimez is a free suite of timezone tools built for a global audience. We provide timezone conversion between 1,332 pairs, a world clock covering 200+ cities, a multi-zone meeting planner, sunrise and sunset calculations, a DST change calendar, stock market hours tracker, countdown timers, date calculators, and educational content about how time zones work. All tools are free to use with no account required.
Our Data Sources
- IANA Time Zone Database — The authoritative source for timezone rules, UTC offsets, and DST transition dates maintained by ICANN. Used by every major operating system and programming language. iana.org/time-zones
- SunCalc — An open-source JavaScript library implementing NOAA solar position algorithms for calculating sunrise, sunset, twilight phases, solar noon, golden hour, moonrise, and moonset. mourner.github.io/suncalc
- Official Exchange Websites — Stock market trading hours (NYSE, NASDAQ, LSE, TSE, and others) are sourced from each exchange's official published schedules, including pre-market and after-hours sessions where applicable.
How We Calculate
- Timezone conversions use IANA standard offsets via the date-fns library with its timezone extension. Conversions account for DST transitions automatically based on the selected date.
- Sunrise and sunset times use SunCalc's implementation of NOAA solar position algorithms, calculating sun altitude based on geographic coordinates, date, and atmospheric refraction. Twilight phases (civil, nautical, astronomical) and moon data are computed using the same algorithms.
- DST transitions are pre-computed for 2 years ahead using the IANA database rules. Each transition includes the exact date, direction (spring forward or fall back), and the UTC offset change.
Accuracy
Timezone conversions are accurate to the second, reflecting the latest IANA database rules including historical and upcoming DST changes. Sunrise and sunset calculations are accurate to within 2 minutes for most locations between 60°N and 60°S latitude. Accuracy may decrease for extreme latitudes near polar regions. Market trading hours reflect standard schedules and may differ on exchange holidays.
Update Frequency
Timezone data is updated with each IANA database release (typically 3-4 times per year as governments announce timezone rule changes). DST schedules are verified annually. Market hours are reviewed quarterly. City data and educational content are updated on an ongoing basis.
Contact & Corrections
Found an error or have a suggestion? Email us at hello@bestimez.com. We review all reports and aim to correct data issues promptly.