14 Dec 2000
28 Apr 2013
With Time-Conversion and Viewing Guides
|Use these links to data for past, current, and predicted events.|
EQUINOX & SOLSTICE
(US NAVAL OBSERVATORY)
APHELION & PERIHELION
(US NAVAL OBSERVATORY)
The calendar below lists approximate dates of seasonal events only.
WARNING: To avoid permanent eye injury and possible blindness, never look directly at the sun, either with the naked eye or through any kind of lens. To view the sun safely and inexpensively, use a pinhole projection as described in "viewing a solar eclipse."
CAUTION: To avoid equipment damage, do not point a camera, binoculars, or telescope directly at the sun without a proper solar filter.
|2-6 January||Perihelion||Earth at orbital position closest to sun.||Earth's orbital velocity is faster, and the sun is closer and so appears slightly larger, than at any other time of year.|
|04 January||Quadrantid meteor shower||Quadrantid meteors radiate from northern sky. (Visible in northern hemisphere only.)||Viewing a meteor shower.|
|20 or 21 March||Equinox||
Sun passes northward over Equator.
|Hours of daylight and darkness approximately equal at most latitudes. Sunrise at north pole, sunset at south pole.|
|20 or 21 June||Solstice||Sun directly above Tropic of Cancer.||Maximum hours of daylight (summer solstice) north of equator; minimum hours of daylight (winter solstice) south of equator.|
|3-7 July||Aphelion||Earth at orbital position farthest from sun.||Earth's orbital velocity is slower, and the sun is more distant and so appears slightly smaller, than at any other time of year.|
|12-16 August||Perseid meteor shower||Anticipated peak shower activity.||Viewing a meteor shower.|
|22 or 23 September||Equinox||Sun passes southward over Equator.||Hours of daylight and darkness approximately equal at most latitudes. Sunrise at south pole, sunset at north pole.|
|18 November||Leonid meteor shower||Anticipated peak shower activity.||Viewing a meteor shower.|
|14 December||Geminid meteor shower||Anticipated peak shower activity.||Viewing a meteor shower.|
|21 December||Solstice||Sun directly above Tropic of Capricorn.||Minimum hours of daylight (winter solstice) north of equator; maximum hours of daylight (summer solstice) south of equator.|
GMT - LOCAL TIME CONVERSION
Observers in North America can use the following table to convert Greenwich Mean Time (GMT) to local Standard or Daylight Saving time:
|Standard||GMT - 9 hr.||GMT - 8 hr.||GMT - 7 hr.||GMT - 6 hr.||GMT - 5 hr.||GMT - 4 hr.|
|Daylight-Saving||GMT - 8 hr.||GMT - 7 hr.||GMT - 6 hr.||GMT - 5 hr.||GMT - 4 hr.||GMT - 3 hr.|
Observers in the Western Hemisphere should use the following procedure to ensure that both time and date are correctly converted from GMT:
|1.||FIND predicted GMT time and date of event on calendar.||Event predicted for 1 June at 02:45 GMT.||GMT = 02:45||1 June|
|2.||CHOOSE appropriate local-time conversion figure from table above.||For 1 June in Chicago, select Central Daylight Time figure.||CDT = GMT - 5||1 June|
|3.||SUBTRACT local-time conversion figure from GMT hours. If result is 0 or greater, skip to step 5.||Subtract 05:00 from 02:45.||02:45 - 05:00 = -03:45||1 June|
|4.||a||IF result of step 3 is negative (less than 0), add 24 hours.||Because -03:45 is negative, algebraically add 24 hours.||-03:45 + 24:00 = 21:45||1 June|
|b||IF 24 hours were added in step 4a, subtract 1 day from GMT date.||Because 24 hours were added, use calendar date preceding GMT date.||1 June - 1 day = 31 May||31 May|
|5.||FINISHED!||Local time and date = CDT||21:45 (9:45 PM)||31 May|
Observers in the Eastern Hemisphere can use a similar procedure, except that they must add hours to GMT depending on their local time zone. If the total hours exceed 24, then subtract 24 hours and increment to the following date.
24-HOUR TO AM-PM TIME CONVERSION
To convert from 24-hour to 12-hour format, do the following:
|If 24-hour time is...||00:00 - 00:59||...add 12 hours...||...12-hour time is...||AM||12:00 M - 12:59 AM|
|01:00 - 11:59||...then...||1:00 AM - 11:59 AM|
|12:00 - 12:59||...then...||PM||12:00 N - 12:59 PM|
|13:00 - 23:59||...subtract 12 hours...||1:00 PM - 11:59 PM|