Timezones
The basic information for this table is found in Randy Jacobson's work, "Time Zones for Earhart Radio Message Database."
- From local to GMT
- To determine how to get back to GMT time from a local time, always add the offsets given below to get GMT time.
- From GMT to local
- Subtract the value of the offset from GMT to get the local time.
- Math reminders
- When we add negative numbers, the result is the same as subtracting the absolute value of the number from the base.
- 0000 GMT + (-1) = 0000 - 0100 = 2300
- When we subtract negative numbers, the result is the same as adding the absolute value of the number to the base.
- 0000 GMT - (-1) = 0000 + 0100 = 0100
- Dateline
- If you are crossing the dateline, add a day if transiting east to west; subtract a day if transiting west to east.
- In the case of their last flight, Earhart and Noonan took off at 1000 hours on 2 July in Lae, which was 0000 GMT on 2 July in Greenwich. After flying for 14 hours from west to east, the aircraft would pass the midnight hour from July 2 to July 3 with respect to Lae, but when it crossed the dateline, it would then be "back" on July 2nd.
- Time Zone Conventions
The convention used in this table for Time Zone values is the opposite of the current UTC convention. To convert to the UTC convention, change all of the positive offsets to negative numbers and all of the negative offsets to positive numbers.
| Ship/Place | Time of TZ Change | Time Zone offset from GMT |
|---|---|---|
| Baker | 11 | |
| Honolulu | 10.5 | |
| Howland | 10.5 | |
| Jarvis | 10.5 | |
| Lae | (-10) | |
| San Francisco | 8 | |
| Washington, DC | 5 | |
| London | (-1) | |
| American Samoa | 11 | |
| CINCUS | 8 | |
| COMINBATFOR | 10.5 | |
| COMDESCOFOR | 8 | |
| COMAIRBASEFOR | 8 | |
| COMBATSHIPS | 8 | |
| COMAIRBATFOR | 8 | |
| Duane | 13 Jan 1937 | 10.5 |
| 15 Jan 0530 | 11 | |
| 24 Jan 1300 | 10.5 | |
| Shoshone | March 10, 0700 | 10.5 (stays 10.5 for duration of first attempt) |
| Itasca | 19 June 0000 | 10.5 |
| 20 June 1400 | 11 | |
| 22 June 1400 | 11.5 | |
| 12 July 1400 | 12 | |
| 14 July 0000 | 11.5 | |
| 20 July 1400 | 11 | |
| 23 July 0800 | 10.5 | |
| Ontario | 17 June 1937 | 0700 11 |
| 18 June 0000 | 12 | |
| 20 June 1100 | (-12) | |
| 22 June 1800 | (-11) | |
| 5 July 0800 | -12 | |
| 7 July 1500 | 12 | |
| 9 July 1500 | 11 | |
| Swan | 1 July 0000 | 11 |
| 6 July 1300 | 11.5 | |
| 10 July 0300 | 11 | |
| 10 July 1700 | 11.5 | |
| 12 July 1900 | 12 | |
| 15 July 0000 | (-12) | |
| Colorado | 3 July 1400 | 10.5 |
| 4 July 4 1300 | 11 | |
| 7 July 1300 | 11.5 | |
| 14 July 1300 | 10.5 | |
|
Lexington |
1 July 1937 | 8 |
| 5 July 1600 | 9 | |
| 7 July 1600 | 10 | |
| 8 July 1030: | 10.5 | |
| 12 July | 11.5 | |
| 21 July | 10.5 |