UTC ↔ local time
See utc-zulu-basics.
- Earth turns 15° of longitude per hour = 4 min per degree (TC AIM GEN 1.5.2).
- Each time zone spans about 15°.
- Canadian zones are west of Greenwich: local runs behind UTC.
Zone offsets (TC AIM Table 1.2; DST = one hour less negative):
| Zone | Standard | DST | Standard meridian (TC AIM GEN 1.5.2) |
|---|---|---|---|
| Newfoundland (NST) | −3.5 | −2.5 | not listed |
| Atlantic (AST) | −4 | −3 | 60°W |
| Eastern (EST) | −5 | −4 | 75°W |
| Central (CST) | −6 | −5 | 90°W |
| Mountain (MST) | −7 | −6 | 105°W |
| Pacific (PST) | −8 | −7 | 120°W |
Conversion (offset is negative going west; use the offset in effect, DST column while DST runs):
| To get | Formula | Example |
|---|---|---|
| Local | UTC + offset | 1500Z Eastern (UTC−5) → 1000 local |
| UTC | local − offset | 0800 Pacific (UTC−8) → 1600Z |
- Date: crossing midnight changes the calendar day.
2000Pacific →0400Zthe next day.0200ZEastern →2100local the previous day.
- Longitude to zone: ÷ 15 = hours behind UTC. 75°W = UTC−5.
Daylight saving time (DST): clocks advance one hour at aerodromes that observe it (TC AIM GEN 1.5.3).
| Canada DST | |
|---|---|
| Starts | 0200 local, second Sunday in March |
| Ends | 0200 local, first Sunday in November |
- DST shifts the local-to-UTC offset, not UTC.
- UTC (Zulu) never changes. METARs, TAFs, flight plans always in Z (AIP Canada GEN 2.1.2). DST changes only the local reading for that Z time.
- Not all aerodromes observe DST. CFS/CWAS Aerodrome/Facility Directory, subheading REF, marks observers DT or ‡.
Trap: wrong offset direction (west: subtract for local, add for UTC), forgetting Newfoundland's half hour, missing date rollover, using the standard offset during DST (or the DST offset outside March-to-November), Z time shifting with DST, or assuming every aerodrome observes DST.
References
- TC AIM GEN 1.5.3
- TC AIM GEN 1.5.2
- AIP Canada GEN 2.1.2