Rules

Next running

2026-04-18 12:00 UTC to 2026-04-19 12:00 UTC (24 hours)
Always the 3rd weekend in April.

Rules Submit log Logger files

At a glance

Bands: 160/80/40/20/15/10 m
Modes: CW, SSB (and Mixed)
Exchange: RST + UTC Time OffsetCode (e.g. 599 0100E, 59 0330W, 599 0000Z)
Work each station once per band per mode (CW and SSB count separately)
Recommended CQ call: CQ TZ
Multipliers: UTC offsets per band + Mirror bonus

Why it’s different

Instead of DXCC entities or zones, WTZC rewards time-zone diversity. A short path around the “24‑hour clock” is used for points, so chasing the far side of the world is always valuable.

Organiser

WTZC Committee
Official site: wtzc-contest.com
Cabrillo contest name: WTZC

Contest name: WTZC – World Time Zone Challenge
Sponsor: WTZC Committee
Website: wtzc-contest.com
Cabrillo name: WTZC

1. Date & time

WTZC runs every year on the 3rd weekend in April, from 12:00 UTC Saturday to 12:00 UTC Sunday (24 hours), single continuous operating window.

2. Bands & modes

Bands: 160 m, 80 m, 40 m, 20 m, 15 m, 10 m
Modes: CW, SSB. (Category “Mixed” = both CW and SSB used.)
Digital modes: not permitted.

Recommended CQ call: call CQ TZ (or answer stations calling CQ TZ) during the contest.

3. Exchange

RST + OffsetCode

OffsetCode format: HHMM followed by a single letter indicating the sign of your UTC offset:

UTC+ (east of UTC) → HHMME, e.g. 0100E = UTC+01:00, 0530E = UTC+05:30
UTC− (west of UTC) → HHMMW, e.g. 0500W = UTC−05:00, 0330W = UTC−03:30
UTC±00:00 → 0000Z (only this “Z” form is valid; never 0000E or 0000W)

The full list of valid HHMME / HHMMW OffsetCodes accepted in the contest is given in section 10 – Valid UTC offsets below.

Daylight saving time / summer time: use your standard legal UTC offset at the time of the contest. That means if your local law applies DST/summer time on the contest weekend, you send the DST-adjusted UTC offset (e.g. the UK is typically 0100E during BST in April).

4. QSO rules

Each station may be worked once per band per mode (one CW + one SSB on the same band are allowed).
A CW QSO and an SSB QSO with the same station on the same band are not duplicates and both may count (subject to correct exchange).
If an exchange is busted (invalid offset, not on the official list, or otherwise incorrect): the QSO counts as 0 points and earns no multiplier credit.

5. Scoring

5.1 QSO points

Picture all UTC offsets arranged around a 24‑hour clock. Let Δ be the shortest distance around that clock between your UTC offset and the other station’s UTC offset (UTC+ is hhMME, UTC− is hhMMW. For example London will be 0100E). Then:

QSO points = 1 + floor( Δ / 60 )

The 24‑hour clock wraps around, so you always measure the short way. Here, Japan (0900E) and French Polynesia (0900W) are 18 h apart the long way round via 0Z, but the short path via ±12 is only 6 h → 7 points.

The same pairing, drawn on a 3D globe. The bright curve traces the great‑circle path across Earth's surface (≈ 11 000 km) — the actual way HF radio waves travel between the two stations, following the planet's curvature. The faint dashed line is the straight chord through the Earth, which of course is not a real radio path. Visually, this is the same "short way" the 24‑hour clock above measures as 6 hours.

Because the shortest 24‑hour distance is used, Δ is always 0–12 hours (0–720 minutes), so points range from 1 (same offset) to 13 (12 hours apart).

Examples

Your offset	Other station	Shortest Δ	Points
`0000Z`	`0300E`	3h	1 + 3 = 4
`0530E`	`0800E`	2h30m	1 + floor(2.5) = 3
`1100E`	`1100W`	2h (not 22h)	1 + 2 = 3
`1245E`	`0345W`	7h30m (not 16h30m)	1 + 7 = 8

5.2 Multipliers

Offsets are multipliers per band. Each unique received OffsetCode on a band counts as 1 multiplier on that band.

5.3 Mirror bonus

For each HHMM where you have worked at least one HHMME and at least one HHMMW anywhere in your log, add +1 bonus multiplier.

0000Z does not participate in mirror pairs.

5.4 Final score

Final score = (total QSO points) × (total band multipliers + mirror bonus multipliers)

6. Entry categories

Operator: Single Operator

Mode: CW / SSB / Mixed

Power:

QRP: up to 20 W output
Low: up to 100 W output
High: above 100 W, up to your licence limit

No Assisted / Unassisted category separation.

7. Assistance, spotting & remote operation

DX cluster / spotting networks: allowed
Self-spotting: allowed
Remote operation: not allowed (transmitter and operator must be co-located at the station’s operating site)

8. Logs

Format: Cabrillo 3.0 required
Deadline: within 7 days after contest end
Submission: web upload form (see Submit Log)
Penalties (log checking): Not-in-log or busted call → QSO removed and any associated multiplier removed. Busted exchange (offset) → 0 points and no multiplier credit for that QSO.

9. Awards

Certificates: PDF download
Plaques: yes (details published each year)
Special awards: Most Offsets Worked, Best Mirror Hunter, Top score per UTC offset

10. Valid UTC offsets (fixed list)

Below is the list of valid exchange OffsetCodes. The key rule is unchanged: send the UTC offset your country is actually using on contest day — i.e. the DST / summer‑time offset wherever your country applies it on the contest weekend.

The map above shows standard time zones and is for geographic reference only. The DXCC examples in the table are given for the contest weekend (3rd weekend of April), so most of Europe, the UK/Ireland, the USA and Canada appear at their DST / summer‑time offset, while Australia, New Zealand, Lord Howe Is. and Chatham Is. are already back on standard time by that date.

OffsetCode	UTC offset	DXCC examples on contest weekend
`1200W`	UTC−12:00	Baker & Howland Is. (KH1)
`1100W`	UTC−11:00	American Samoa (KH8), Niue (ZK2)
`1000W`	UTC−10:00	Hawaii (KH6), Tahiti – French Polynesia (FO), Cook Is. (ZK1)
`0930W`	UTC−09:30	Marquesas Is. (FO/M)
`0900W`	UTC−09:00	French Polynesia – Gambier Is. (FO/G)
`0800W`	UTC−08:00	Alaska (KL7) on AKDT, Pitcairn (VP6)
`0700W`	UTC−07:00	USA Pacific W6 on PDT, Canada VE7 on PDT, USA Arizona (W7/AZ)
`0600W`	UTC−06:00	USA Mountain W7 on MDT, Canada VE6 on MDT, Mexico (XE), Guatemala (TG), Belize (V3)
`0500W`	UTC−05:00	USA Central W5 on CDT, Canada VE4/VE5 on CDT, Colombia (HK), Peru (OA), Ecuador (HC), Panama (HP)
`0400W`	UTC−04:00	USA Eastern W4 on EDT, Canada VE3/VE2 on EDT, Cuba (CO) on CDT, Puerto Rico (KP4), Dominican Rep. (HI), Venezuela (YV), Bolivia (CP), Chile (CE), Barbados (8P)
`0330W`	UTC−03:30	— (Newfoundland is on NDT during the contest → see `0230W`)
`0300W`	UTC−03:00	Argentina (LU), Uruguay (CX), Brazil (PY), Suriname (PZ), French Guiana (FY), Falkland Is. (VP8)
`0230W`	UTC−02:30	Canada Newfoundland (VO1/VO2) on NDT
`0200W`	UTC−02:00	Fernando de Noronha (PY0F), South Georgia (VP8G)
`0100W`	UTC−01:00	Cape Verde (D4) (Azores are on WEST = `0000Z` during the contest)
`0000Z`	UTC±00:00	Iceland (TF), Azores (CU) on WEST, Senegal (6W), The Gambia (C5), Ghana (9G), Burkina Faso (XT)
`0100E`	UTC+01:00	United Kingdom (G) on BST, Ireland (EI) on IST, Portugal mainland (CT) on WEST, Canary Is. (EA8) on WEST, Morocco (CN), Tunisia (3V), Algeria (7X), Nigeria (5N)
`0200E`	UTC+02:00	Germany (DL), France (F), Italy (I), Spain (EA), Netherlands (PA), Poland (SP), Sweden (SM), Norway (LA), Switzerland (HB9) — all on CEST; South Africa (ZS), Libya (5A), Egypt (SU)
`0300E`	UTC+03:00	Romania (YO) on EEST, Greece (SV) on EEST, Bulgaria (LZ), Finland (OH), Ukraine (UR), Estonia/Latvia/Lithuania (ES/YL/LY), Cyprus (5B), Israel (4X) on IDT, Turkey (TA), European Russia – Moscow (UA), Kenya (5Z), Jordan (JY)
`0330E`	UTC+03:30	Iran (EP)
`0400E`	UTC+04:00	Armenia (EK), Georgia (4L), Azerbaijan (4J), UAE (A6), Oman (A4), Mauritius (3B8), Reunion (FR)
`0430E`	UTC+04:30	Afghanistan (T6)
`0500E`	UTC+05:00	Pakistan (AP), Maldives (8Q), Uzbekistan (UK), Turkmenistan (EZ), Tajikistan (EY), Kazakhstan (UN)
`0530E`	UTC+05:30	India (VU), Sri Lanka (4S)
`0545E`	UTC+05:45	Nepal (9N)
`0600E`	UTC+06:00	Bangladesh (S2), Bhutan (A5), Kyrgyzstan (EX)
`0630E`	UTC+06:30	Myanmar (XZ), Cocos (Keeling) Is. (VK9C)
`0700E`	UTC+07:00	Thailand (HS), Vietnam (3W), Cambodia (XU), Laos (XW), Indonesia – west (YB)
`0800E`	UTC+08:00	China (BY), Taiwan (BV), Hong Kong (VR), Singapore (9V), Malaysia (9M), Philippines (DU), Western Australia (VK6), Brunei (V8)
`0845E`	UTC+08:45	Australia – Eucla (VK)
`0900E`	UTC+09:00	Japan (JA), Korea (HL), Indonesia – east (YB), Palau (T8), Timor‑Leste (4W)
`0930E`	UTC+09:30	Australia – Northern Territory (VK8), Australia – South Australia (VK5) off DST by mid‑April
`1000E`	UTC+10:00	Eastern Australia VK2/3/4/7 back on AEST (off AEDT), Papua New Guinea (P2), Guam (KH2)
`1030E`	UTC+10:30	Australia – Lord Howe Is. (VK9L) on LHST (off LHDT)
`1100E`	UTC+11:00	New Caledonia (FK), Solomon Is. (H44), Vanuatu (YJ), Norfolk Is. (VK9N)
`1200E`	UTC+12:00	New Zealand (ZL) on NZST (off NZDT), Fiji (3D2), Kiribati – Gilbert Is. (T30), Marshall Is. (V7), Tuvalu (T2)
`1245E`	UTC+12:45	New Zealand – Chatham Is. (ZL7) on Chatham Standard Time
`1300E`	UTC+13:00	Tonga (A3), Tokelau (ZK3), Samoa (5W)
`1400E`	UTC+14:00	Kiribati – Line Is. (T31)