Convert Hawaii Standard Time to Greenwich Mean Time
Instantly convert Hawaii Standard Time (HST) to Greenwich Mean Time (GMT) with our free online calculator.
Hawaii Standard Time
07:20:49 PM
Tue, Jun 23 (HST)
Greenwich Mean Time
05:20:49 AM
Wed, Jun 24 (GMT)
Convert a Specific Time
24-Hour Comparison
| HST | GMT |
|---|---|
| 12:00 AM | 10:00 AM |
| 1:00 AM | 11:00 AM |
| 2:00 AM | 12:00 PM |
| 3:00 AM | 1:00 PM |
| 4:00 AM | 2:00 PM |
| 5:00 AM | 3:00 PM |
| 6:00 AM | 4:00 PM |
| 7:00 AM | 5:00 PM |
| 8:00 AM | 6:00 PM |
| 9:00 AM | 7:00 PM |
| 10:00 AM | 8:00 PM |
| 11:00 AM | 9:00 PM |
| 12:00 PM | 10:00 PM |
| 1:00 PM | 11:00 PM |
| 2:00 PM | 12:00 AM(+1d) |
| 3:00 PM | 1:00 AM(+1d) |
| 4:00 PM | 2:00 AM(+1d) |
| 5:00 PM | 3:00 AM(+1d) |
| 6:00 PM | 4:00 AM(+1d) |
| 7:00 PM | 5:00 AM(+1d) |
| 8:00 PM | 6:00 AM(+1d) |
| 9:00 PM | 7:00 AM(+1d) |
| 10:00 PM | 8:00 AM(+1d) |
| 11:00 PM | 9:00 AM(+1d) |
How to Convert Hawaii Standard Time to Greenwich Mean Time
Formula
To convert Hawaii Standard Time (HST) to Greenwich Mean Time (GMT): Convert HST to GMT
About Hawaii Standard Time (HST)
Hawaii Standard Time (HST, IANA: Pacific/Honolulu) is the time zone for the State of Hawaii and the Aleutian Islands of Alaska west of 169.5°W. HST is UTC-10:00 year-round and does not observe Daylight Saving Time per Hawaii Revised Statutes §1-31 (Hawaii opted out of the Uniform Time Act of 1966). When the US mainland switches to Daylight Saving Time in March, the offset from Hawaii to the West Coast (Pacific Time) becomes 3 hours instead of the standard 2 hours. Honolulu sees solar noon at approximately 12:30 PM HST in summer. HST is the same offset as Cook Island Time (CKT) and Tahiti Time (TAHT) in French Polynesia, allowing easy mental conversion across the central Pacific. Time-sensitive activities affected by HST include Pacific tsunami warning system coordination per NOAA NTWC, US military operations from Joint Base Pearl Harbor-Hickam, and the Mauna Kea astronomical observatories' nightly observing schedules.
About Greenwich Mean Time (GMT)
Greenwich Mean Time (GMT, IANA: Europe/London) is the historic and current civil time of the United Kingdom (during winter), Ireland (during winter), Portugal mainland (during winter), Iceland (year-round), and most West African countries. GMT is set at UTC+0 — the time on the Prime Meridian (0° longitude) running through the Royal Observatory in Greenwich, southeast London. Established as the global time reference by the 1884 International Meridian Conference in Washington DC, GMT served as the world's primary civil-time reference from 1884 until 1972 when UTC (Coordinated Universal Time) was adopted as the new precision standard. The UK switches from GMT to British Summer Time (BST = UTC+1) at 01:00 GMT on the last Sunday of March and back to GMT at 02:00 BST on the last Sunday of October per EU Directive 2000/84/EC (UK retained this schedule after Brexit). GMT affects: London Stock Exchange (LSE) trading hours, BBC World Service broadcast time-stamps, all aviation NOTAMs and weather METARs which use UTC = GMT, and ICAO + IMO worldwide maritime/aviation coordination.