Timezone Helper

Convert times between any time zones, plan global meetings, check DST status.
Zero dependencies — all data built-in, works in any environment.

Full city-to-timezone mapping: see references/cities.md.

When to use

• - "What time is it in Tokyo right now?"
• "Convert 3pm New York to London time"
• "Schedule a meeting for our team in SF, London and Singapore"
• "Does Germany observe DST? When does it change?"
• "What's the UTC offset for IST?"
• "Find a time that works for NYC, Berlin and Beijing"

Core concepts

UTC offset

• - UTC+9 = 9 hours ahead of UTC (Tokyo, Seoul)
• UTC-5 = 5 hours behind UTC (New York EST, Lima)
• UTC+0 = same as UTC (London GMT, Reykjavik)

DST (Daylight Saving Time)

• - Northern Hemisphere (US, Europe, etc.): spring forward, fall back

• - Southern Hemisphere (Australia, NZ, etc.): opposite — DST in Oct–Apr
• No DST: China, Japan, India, most of Africa, Middle East, Southeast Asia

Always confirm the current date when doing DST-sensitive conversions.

Step 1: Resolve city/region to IANA timezone

Use the table in references/cities.md to map user input to an IANA zone.
Common shortcuts to recognize:

EST / ET    → America/New_York  (UTC-5 standard, UTC-4 DST)
CST (US)    → America/Chicago   (UTC-6 standard, UTC-5 DST)
MST         → America/Denver    (UTC-7 standard, UTC-6 DST)
PST / PT    → America/Los_Angeles (UTC-8 standard, UTC-7 DST)
GMT / UTC   → UTC               (UTC+0, no DST)
BST         → Europe/London     (UTC+1, summer only)
CET / CEST  → Europe/Paris      (UTC+1 standard, UTC+2 DST)
IST         → Asia/Kolkata      (UTC+5:30, no DST)
CST (China) → Asia/Shanghai     (UTC+8, no DST)
JST         → Asia/Tokyo        (UTC+9, no DST)
AEST / AEDT → Australia/Sydney  (UTC+10 standard, UTC+11 DST)

Step 2: Apply UTC offset

Conversion formula:
CODEBLOCK1

If result crosses midnight: adjust date ±1 day accordingly.

Example:

Convert 14:00 New York (EST, UTC-5) → Tokyo (JST, UTC+9)
Difference = +9 - (-5) = +14 hours
14:00 + 14h = 28:00 → 04:00 next day Tokyo

Step 3: Check DST status

Before finalizing, verify whether DST is currently active for each zone.
If the user's current date is near a DST transition, note the change.

DST transitions (approximate):

US (spring forward):  Second Sunday of March,    02:00 → 03:00
US (fall back):       First Sunday of November,  02:00 → 01:00
EU (spring forward):  Last Sunday of March,      01:00 UTC → 02:00 UTC
EU (fall back):       Last Sunday of October,    01:00 UTC → 00:00 UTC
Australia/Sydney:     First Sunday of October,   02:00 → 03:00
Australia/Sydney:     First Sunday of April,     03:00 → 02:00

Output formats

Single conversion

World clock (current time)

Meeting planner

DST query

🕐 DST Information: Germany (Europe/Berlin)
━━━━━━━━━━━━━━━━━━━━
Current offset:    UTC+1  (CET — Central European Time)
DST observed:      Yes
DST offset:        UTC+2  (CEST — Central European Summer Time)
Spring forward:    Last Sunday of March   → clocks +1h at 02:00
Fall back:         Last Sunday of October → clocks -1h at 03:00
2026 transitions:  Mar 29 (→ CEST)  /  Oct 25 (→ CET)

Meeting planner logic

When finding meeting overlap across zones:

CODEBLOCK8

Notes

• - Always ask for or confirm the current date when DST status matters
• "IST" is ambiguous: could be India (UTC+5:30), Israel (UTC+2), or Ireland (UTC+0/+1) — clarify with user if context is unclear
• "CST" is ambiguous: US Central (UTC-6/-5) or China Standard (UTC+8) — resolve from context
• Half-hour and 45-minute offsets exist: India (UTC+5:30), Iran (UTC+3:30), Nepal (UTC+5:45), Australia/Lord Howe (UTC+10:30/+11)
• For precise current-time queries, note that this skill provides static offset data; the actual current time depends on the system clock