Question 1

How do I convert a meeting time between timezones without getting it wrong?

Accepted Answer

Use jslet's Timezone Converter: enter the source datetime, pick the source timezone (e.g., US/Pacific), pick the target timezone (e.g., Europe/London), and the tool shows the converted time instantly. It also displays each timezone's current UTC offset (e.g., UTC-7 for Pacific Daylight Time, UTC+1 for British Summer Time) and whether DST is active — so you can verify the conversion makes sense. The most common timezone mistake is assuming that '2 PM my time' maps to a fixed offset year-round. DST transitions make this wrong: San Francisco (US/Pacific) is UTC-8 in winter but UTC-7 in summer. A meeting scheduled as '10 AM Pacific' in January is 6 PM London; in July, it is 6 PM London (because both regions observe DST, but they don't switch on the same day — there are 1-3 weeks per year when the offset is different by an hour). The tool always uses the IANA timezone database (the same database Linux servers and browsers use), so DST transitions are handled correctly for the datetime you pick. All conversion happens in your browser.

Question 2

Why do I see US/Pacific, America/Los_Angeles, and PST — which timezone name should I use?

Accepted Answer

Use IANA timezone identifiers (like America/Los_Angeles or Europe/London) — they are the only standard that correctly handles DST transitions and historical timezone changes. Three naming systems exist and they're easily confused: (1) IANA identifiers (America/Los_Angeles) — the correct choice. They encode the geographic region, so the system knows DST rules for that location historically and into the future. (2) POSIX abbreviations (PST, PDT, EST, EDT) — ambiguous and dangerous. 'CST' could mean China Standard Time (UTC+8), Central Standard Time US (UTC-6), or Cuba Standard Time (UTC-5). Never store or transmit these as authoritative identifiers. (3) UTC offsets (UTC-8, UTC+5:30) — useful for display, but offset alone loses DST information. India is always UTC+5:30 (no DST), but the US East Coast is UTC-5 in winter and UTC-4 in summer. jslet's converter uses IANA identifiers in the dropdown and shows both the current offset and the abbreviation for context. US/Pacific is a deprecated alias for America/Los_Angeles — it still works but the canonical form is America/Los_Angeles.

Question 3

How does daylight saving time (DST) affect timezone conversion, and how do I avoid scheduling errors around DST transitions?

Accepted Answer

DST creates two types of scheduling traps. Spring-forward gap: in the US, clocks jump from 1:59 AM to 3:00 AM on the second Sunday in March. A meeting scheduled for 2:30 AM on that day literally doesn't exist — no clock ever shows 2:30 AM in that timezone on that date. If you schedule a recurring event at 2:30 AM daily in US/Eastern, the cron job or calendar must have a policy for the missing hour (skip, run at 3:00, or error). Fall-back ambiguity: on the first Sunday in November, 1:30 AM happens twice — once at UTC-4, then again an hour later at UTC-5. If you schedule something at 1:30 AM on that day, which one do you mean? The IANA database resolves this by convention: the first occurrence (UTC-4, DST active) is used for the initial timestamp; the second occurrence (UTC-5, standard time) requires an explicit UTC offset. For practical scheduling: avoid scheduling anything between 1:00–3:00 AM local time in DST-observing regions. If you must, use UTC as the canonical time and convert to local time for display only. The timezone converter shows DST status for both source and target timezones so you can spot transition days before they cause problems.

Best practice	Store all times as UTC. Convert to local timezone only at the presentation layer.
Common pitfall	Using fixed offsets (`+05:30`) instead of IANA names —DST rules change over time.

🟢📖 Understanding Timezone Conversion