Timezone Helper

Time zone conversion, world clock, and meeting planner. Use when the user asks about current time in a city, needs to convert time between zones, wants to sc...

Security Scan

The skill is an instruction-only, offline timezone/conversion helper whose requirements and instructions match its stated purpose and request no credentials or installs.

Purpose & Capability

Name and description (time zone conversion, world clock, meeting planner) align with the SKILL.md and the included references/cities.md. The skill requests no binaries, env vars, or installs — consistent with its stated 'fully offline' design.

Instruction Scope

Runtime instructions are self-contained: resolve city → IANA zone using references/cities.md, apply UTC offset and DST rules, and present formatted outputs. The instructions do not request unrelated files, environment variables, or external network endpoints. Note: DST guidance is approximate and the document correctly asks agents to confirm dates for DST-sensitive conversions and to disambiguate abbreviations like 'IST'.

Install Mechanism

No install spec and no code files; this is instruction-only so nothing will be downloaded or written to disk during install. Low installation risk.

Credentials

No environment variables, credentials, or config paths are requested. The skill does not ask for unrelated secrets or access.

Persistence & Privilege

always is false and the skill does not request persistent privileges or modify other skills or system settings. Normal user-invocable/autonomous invocation settings apply.

Assessment

This skill appears coherent and low-risk: it is offline, requires no credentials, and confines itself to the included city→IANA mapping and conversion logic. Before relying on it for critical scheduling: (1) confirm the exact date and disambiguate timezone abbreviations (e.g., IST, CST), (2) be aware DST rules can change and the SKILL.md contains approximate transition rules, and (3) verify that the specific city you need is present and correctly mapped in references/cities.md. If you need authoritative, up-to-the-minute DST/zone data for legal or safety-critical scheduling, prefer an official time service or system timezone database.

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"

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Core concepts

UTC offset

Every timezone is expressed as UTC±HH:MM.

• 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)

Some regions shift clocks ±1 hour seasonally:

• Northern Hemisphere (US, Europe, etc.): spring forward, fall back
  • US: second Sunday March → first Sunday November
  • EU: last Sunday March → last Sunday October
• 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:

Target time = Source time + (Target UTC offset) - (Source UTC offset)

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

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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

🌍 Time Zone Conversion
━━━━━━━━━━━━━━━━━━━━
Source:  3:00 PM  Wed, Mar 20  —  New York (EST, UTC-5)
Target:  8:00 PM  Wed, Mar 20  —  London (GMT, UTC+0)
         4:00 AM  Thu, Mar 21  —  Tokyo (JST, UTC+9)
         1:00 AM  Thu, Mar 21  —  Singapore (SGT, UTC+8)

World clock (current time)

🕐 Current World Time  (based on: 15:00 UTC)
━━━━━━━━━━━━━━━━━━━━
🇺🇸  New York       10:00 AM  Wed  (EST, UTC-5)
🇬🇧  London         15:00     Wed  (GMT, UTC+0)
🇩🇪  Berlin         16:00     Wed  (CET, UTC+1)
🇮🇳  Mumbai         20:30     Wed  (IST, UTC+5:30)
🇨🇳  Beijing        23:00     Wed  (CST, UTC+8)
🇯🇵  Tokyo          00:00     Thu  (JST, UTC+9)
🇦🇺  Sydney         02:00     Thu  (AEDT, UTC+11)

Meeting planner

📅 Meeting Planner
━━━━━━━━━━━━━━━━━━━━
Participants:  San Francisco  /  London  /  Singapore

Option A — Best for SF + London:
  San Francisco   09:00 AM  (PST, UTC-8)   ✅ work hours
  London          17:00     (GMT, UTC+0)   ✅ end of day
  Singapore       01:00 AM  (SGT, UTC+8)   ❌ midnight

Option B — Best for London + Singapore:
  San Francisco   01:00 AM  (PST, UTC-8)   ❌ midnight
  London          09:00     (GMT, UTC+0)   ✅ work hours
  Singapore       17:00     (SGT, UTC+8)   ✅ work hours

No perfect overlap exists. Recommended compromise:
  San Francisco   06:00 AM  ⚠️  early
  London          14:00     ✅
  Singapore       22:00     ⚠️  late evening

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:

1. Define "work hours" as 09:00–18:00 local time
2. Define "acceptable" as 07:00–21:00 local time
3. Convert each hour of the day to all participants' local times
4. Score each UTC hour:
   - All in work hours  → ✅ ideal
   - All in acceptable  → ⚠️  workable
   - Any outside 07-21  → ❌ avoid
5. Present top 2-3 options with clear local times
6. If no ideal slot exists, say so explicitly and suggest best compromise

---

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